(You can download the latest version of WordPress Hook Sniffer here. Please read the readme.txt file for important usage and installation notes.)

After the bug fixes, the most noticeable improvement is that you no longer need to manually install the modified plugin.php file—the file that gives hook sniffer its abilities. The plugin now automatically installs the modified plugin.php file upon plugin activation and then reinstalls the original, stock WP version of the /wp-includes/plugin.php file upon plugin deactivation. This means that when you deactivate the plugin, you can rest assured that WP Hook Sniffer no longer has any influence over the operation of WordPress.

As there are important differences between the /wp-includes/plugin.php files of WP 2.9.2 and WP 3.0, WP Hook Sniffer now requires WordPress 3.0. Upon activation, an automatic version check is performed to make sure that WP Hook Sniffer is installed on the proper version of WordPress. If the plugin is installed on an older version of WordPress, it will not run. A warning message is displayed in the Plugins directory and in the WP Hook Sniffer Settings screen.

Also, I’ve versioned the modified plugin.php file that comes with WP Hook Sniffer. Now, when you activate the plugin, it runs a check to make sure that the proper version of the modified plugin.php file is installed in /wp-includes.

Finally, I added a CSS file to improve proper code separation–the older version simply had inline CSS definitions–and renamed all CSS selectors to make them unique to the plugin.

If WordPress Hook Sniffer has become an indispensable tool in your WP plugin development toolkit, please donate to help me keep this plugin updated and its sniffer healthy! Thank you!

Sponsorship Levels

Supporter $15.00 Donor $25.00 Sponsor $50.00 Benefactor $100.00 Patron $250.00 Open Source Angel $500.00 Holy Cow! $1,000.00

If you are a corporate user, consultant, plugin developer, or theme designer and profit from using my plugin, please consider donating at one of the upper levels. Thank you!

I have been having a few issues with BuddyPress development over the past week. I went through all the usual techniques to isolate the issue, finally deactivating all my 3rd-party plugins. But, the issue remained. Finally, I wondered about my WordPress Hook Sniffer plugin. I realized that although it was deactivated, it might be negatively affecting the operation of WordPress if the modified plugin.php file that comes with the plugin had issues. I replaced the modified version of plugin.php with the original one that ships with my version of WordPress, and bingo, the issues went away. All I could think was crap—especially as I say this in the installation instructions:

“The modifications to WordPress’ standard Plugin API file are used exclusively for WordPress Hook Sniffer. They should not affect the functioning of the rest of WordPress.”

In fact, this statement is still technically correct. The culprit is that when I updated the modified plugin.php file for last week’s version 0.13 update to the WP Hook Sniffer, I failed to use the proper base plugin.php file. I used the one that ships with WP 2.9.2 and not WP 3.0. Even though I thought I had done a sufficient parity check between these two files, I had failed to notice a few important changes.

WordPress Core Developers please note: if you change a function you should indicate as much in the inline documentation. Please use the @version PHPDocumenter tag to indicate that the function has changed. The @since tag version indicator is not helpful if the function has changed.

What issues did I have that caused me to discover this problem? The WordPress “wp” action hook was not firing. Yep. That is a big problem, especially if you are doing development work. Interestingly enough, most of BuddyPress continued to function as expected, except for a few features that used to work but suddenly stopped working—right at the time I installed the updated version of WP Hook Sniffer. Of course, I failed to notice this for several days.

I have gone through the stock plugin.php file–with a very fine-toothed comb–and ferreted out all the changes. I am in the process of updating the modified plugin.php file that WP Hook Sniffer is required to use. I want to make sure that it is adequatley tested before releasing an updated version. Look for the updated version with a fixed plugin.php file to be available either Sunday or Monday.

With this pending update, WordPress Hook Sniffer will require WordPress 3.0. Therefore, if you want to use it in an older version of WordPress, you will have to install Version 0.12 of WP Hook Sniffer. Please note, I will only support the most recent version of WordPress Hook Sniffer.

I apologize if this has caused you to lose valuable development time. I know that I have lost several days of productive coding due to this issue. There were obviously some important changes between WP 2.9.x and WP 3.0. Even though I thought I had properly assessed potential changes within the plugin.php file, I had not. I guess I need more sleep, more caffeine, fewer late-night alien visits, or some combination of those three.

These are not the normal, run-of-the-mill plugins that extend BuddyPress by adding additional functionality for a site’s members, or allow a site administrator to selectively alter the core functionality of BuddyPress. Instead, the plugins that I’m excited about are specifically targeted to providing site administrators and developers with unique services. I call these tools to differentiate them from the general-purpose plugins.

Although there are currently only a handful of such tools available, I hope that these releases indicate a trend. The WordPress ecosystem needs more specialty tools for site administrators and plugin developers.

So, in no particular order of importance, here is a listing of the more interesting plugins that provide useful tools for the site administrator’s or developer’s toolbox.

Developer Tools

WordPress Hook Sniffer: This is a tool I recently released that helps plugin developers determine the sequence in which action and filter functions are fired. It provides a window into the inner workings of the WordPress Plugin API and can help a developer figure out why a custom action or filter hook or function is not working as intended.

Wordpress MU Demo Data Creator: Provides a utility for populating your WPMU development sandbox database with dummy data. Why waste time creating your own dummy data to test your plugins when it can be auto generated for you.

BuddyPress Skeleton Component: This is not a new developer tool. In fact, as an example BuddyPress plugin component, it is the grand progenitor of many BuddyPress plugins.

BuddyPress Template Pack: This is not a developer’s tool per say. But I think it deserves listing nonetheless. It is actually a theme designer’s tool that helps make a custom WordPress theme compatible for use as a BuddyPress theme.

Site Administrator Tools

BP System Report: This tool gathers useful network intelligence on a site’s member and group activity. It provides a site administrator with usage trends and statistics, offering important insights into the health of their community.

Import from Ning: I thought I should throw this one in as well as it is a tool that helps social network operators. It provides some utility in helping to migrate a Ning network to BuddyPress. As Ning does not offer too much help in migrating existing networks to competing platforms, this tool is not a panacea to your Ning-networking woes—but it is a great start!

Plugin Developers Need Your Support

Creating a high-quality plugin takes more time than most people realize. In fact, it can take as much time if not more than creating a top-quality theme. But plugin developers rarely receive the same financial rewards that premium theme designers do.

My limited, empirical data shows that with the number of downloads of my current three WordPress / BuddyPress plugins, that less than 0.1% (yes, that is less than one-tenth of one percent) bother to donate. If my plugins received poor reviews, that would be understandable. But, as my lowest-rated plugin received a 4.5-star review out of 5, the lack of donations obviously has nothing to do with perceived quality. Note: Although I am a listed contributor to the BuddyPress Skeleton Component, I do not include that as one of my three plugins.

Whereas the greater WordPress community appears to have no issue with spending money on what are called premium themes, there seems to be a disconnect when it comes to supporting the developers of the plugins that help make their communities successful. Yes, great themes definitely provide an important face to a community, but it’s important to remember that plugins– along with the core functionality of WordPress and BuddyPress–provide the foundation to our networks.

So please generously donate to plugin developers and help keep them coding their wonderful plugins be they general purpose or specialty in nature.

As a developer, one of the downsides to Open Source projects like WordPress and BuddyPress is that a significant amount of foundational code is already in place. There are hundreds of functions, classes, methods, and general code that you never actually get to know. Sure, you might call them from within your code, you might know how and when to use them, but you more than likely do not understand how and why they work and what they actually do to accomplish their task.

Why? Because you were (more than likely) not part of the team that wrote the code, that figured out what each function was required to accomplish and in what ways that code would interact with other parts of the foundation.

This is exactly the situation I found myself in several weeks ago as I was trying to figure out why one of my custom do_action events in my BuddyPress Privacy Component was not working as I had expected. My investigation into this issue not only opened my eyes into the inner workings of WordPress’ Plugin API, but also helped me figure out why a few BuddyPress action events were not behaving as intended.

Understanding Hook Firing Sequence

How can you know the firing sequence of action functions or filter functions that you attach to existing WordPress and BuddyPress hooks? Why is this even important?

To answer the second question, read my article, WordPress Hooks, Barbs, and Snags. The answer to the first question is more difficult.

Since many internal WordPress and BuddyPress functions may be tying into the same action or filter hooks, there is no easy way to know the firing sequence of action functions or filter functions. Add to that the fact that 3rd-party external plugins can also tie into these same action or filter hooks and the issue becomes even more murky.

As I had a serious issue with a custom do_action event in my BuddyPress Privacy Component not working as expected, I set out to solve the first question. Although my problem appeared to be with my custom do_action event, I soon discovered that it was caused by another hook to which I had tied in to.

The result of my investigation: a new tool for WordPress and BuddyPress developers called the WordPress Hook Sniffer. What does this plugin do? It helps plugin developers determine the sequence in which action and filter functions are fired, providing a window into the inner workings of the WordPress Plugin API.

As with all of my other WordPress and BuddyPress plugins, this plugin is licensed under the GNU General Public License 3.0 (GPL).

Download WordPress Hook Sniffer and Donate!

You can download the WordPress Hook Sniffer via the WP Plugin Repository. Even more excitingly, you can help me support this plugin, encourage me to create new ones, and enable me to keep living by selecting a sponsorship level below and clicking the “Pay Now” button. Thank you!

Sponsorship Levels

Supporter $15.00 Donor $25.00 Sponsor $50.00 Benefactor $100.00 Patron $250.00 Open Source Angel $500.00 Holy Cow! $1,000.00

If you are a corporate user, consultant, plugin developer, or theme designer and profit from using my plugin, please consider donating at one of the upper levels. Thank you!

Using the Plugin

WARNING: This plugin is to be used only in a development sandbox and not in a production environment. It is intended solely for use by plugin developers to help determine the sequence in which action and filter functions are fired. Use at your own risk. As this plugin should not be installed on an active WordPress-based site (a production site), no support for broken sites will be given. You have been warned!

It is important that you carefully follow the installation instructions in the readme.txt file. There are several crucial steps you must take to make this plugin work.

1. Once installed and activated, you will find a new menu option in the Settings menu
   
2. Clicking on that will bring up the WordPress Hook Sniffer Settings screen. The first thing to do is look in the upper left-hand corner of the screen. See that gratuitous “Please Support My Work” section? Go ahead and select a nice, juicy amount and then click the “Pay Now” button. Your donation (in any amount) is greatly appreciated! Okay, enough begging.
   
3. Next, read the “Usage Notes” section at the end of this article for a few additional bits of important information
4. Finally, select “Enabled” in the Main Sniffer Settings section, choose what data you wish to view in the Output Options section, and then select where you would like the output to go in the Output Location section
5. It’s that easy!

Output Settings Options

Whereas getting the WordPress Hook Sniffer to work is relatively straight forward, interpreting the output is a different story. What does all of that crap stuff mean?

Here is a brief overview of each of the output options and what information it can provide. However, to truly understand how to interpret the output and how best to use it in your development work, you will need to read my article, WordPress Hooks, Barbs, and Snags article.

A. Added Functions

Selecting this option outputs the special WP Hook Sniffer array that holds, in the order in which they were encountered during code execution, all add_action calls and add_filter calls. The file and line number from which a given function was triggered is also provided.

B. Removed Functions

Selecting this option outputs the special WP Hook Sniffer array that holds, in the order in which they were encountered during code execution, all remove_action calls and remove_filter calls. The file and line number from which a given function was triggered is also provided.

C. Action and Filter Function Array

This is the grandaddy, grandmommy, grandchild, Grand Ole Opry of output data. It contains the output of the $wp_filter array, the array that holds all of the added action and filter functions and is used by the do_action and apply_filters functions call to determine function firing order—although there is a twist here. You must read my article WordPress Hooks, Barbs, and Snags article to learn what it is.

D. Action Event Firing Order

This option contains the output of the $wp_actions array. A simple, one dimensional array that holds the sequential listing of all the do_action events that need to be processed. The events within this array used in conjunction with with corresponding data in the $wp_filter array determines the firing sequence of all action functions

E. Action Event Firing Sequence

Selecting this option outputs the special WP Hook Sniffer array that holds the sequential listing of do_action events with their corresponding fired action function(s). This listing shows you exactly the sequence in which each triggered action event fires its hooked action functions.

F. Filter Event Firing Sequence

Selecting this option outputs the special WP Hook Sniffer array that holds the sequential listing of apply_filters events with their corresponding fired filter function(s). This listing shows you exactly the sequence in which each triggered filter event fires its hooked filter functions.

1. Reporting Bugs: If you find bugs or are having issues using this plugin, you can either post a comment in this article or visit the support forum for this plugin. Assistance in providing patches to this plugin is appreciated.
2. Increasing Precision: If you want to see a more precise accounting of the execution time of a given function, you have to edit your php.ini file to increase the precision displayed for floating point numbers. Search your php.ini file for the entry:

   precision = 12

   and change that to:

   ; precision = 12
precision = 16

   As you can see, I like to comment out any changes to my default php.ini settings just in case I decide to revert the changes later. This allows you to do so easily without having to remember or look up what the default setting is supposed to be.

   Save your modified php.ini file and then restart your development server and you should now see the time-executed stamp displaying 6 significant figures instead of 2. This provides a sufficient level of detail.

3. Text Output Issues: If you’re using SSL or are behind a proxy server, you may have issues when selecting to send the output to a text file. There are a few work arounds for this, but suffice it to say that since this plugin is to be used exclusively in a development sandbox environment, I will not be coding these into the plugin. If you must use this plugin with SSL or behind a proxy server, then simply select the screen output option. You can learn more about this in the PHP manual for the fopen function.
4. Screen Output: When printing to screen, it may take a several seconds for output to finish. The output will start just below your theme’s footer.

This article is my exhaustive study of what I thought was a simple little function—the do_action function. It details how WordPress action hooks really work. It is a long, detailed article. If you want to understanding the inner works of the do_action function, then it will be worth your time. Although this article only briefly mentions the apply_filters function, the lessons learned about the do_action function apply equal as well as the coding of these two functions is nearly identical.

This is not a beginners guide to WordPress action and filter hooks. To benefit from this article, you need to understand what hooks are, why you use them, and how to use them.

Hooks, Barbs, and Snags

Before we start, I need to define two terms. You may be wondering about the title of this article, “WordPress Hooks, Barbs, and Snags.” You should already know the definition of a WordPress hook. But what are barbs and snags?

These are two terms I created to classify the following:

Barbs: salient insights about the functioning of WordPress hooks that stick out and grab your attention. Understanding these barbs help you avoid snags. In this sense, a barb is a good thing.

Snags: WordPress hooks that do not execute as expected, not because the do_action or apply_filters functions are misbehaving, but rather because you do not understand how these functions actually work.

The Hook Loop or Where the Issue Gets Complex

When it comes to code, loops can be tricky constructs to properly implement. What seems like a simple, innocuous operation may actually be more complex than meets the eye. This is the case with the do loops in the do_action and apply_filters functions.

There are two key arrays that WordPress uses to determine the firing sequence of actions and filters— the $wp_actions and $wp_filter arrays. These arrays get built throughout the execution of each page load and are not fully populated until page load is complete and PHP stops execution, waiting for its next command.

The $wp_filter Array

The $wp_filter array is where all added action functions and filter functions are stored for future reference and processing by both the apply_filters function and the do_action function. This array is a very-large, multidimensional array nested to four levels. See the snapshot of the partial contents of this massive array.

Here is a snapshot of what is generated in the $wp_filter array just by navigating to the homepage in my particular setup. Your results will vary depending on which plugins you have activated, which theme you’re using, whether you’re running WordPress in single-site or multi-site mode, whether you’re running BuddyPress, whether a user is logged into your site, and of course which versions of WP / BP you currently have installed.

As you can see, there are a lot of action functions and filter functions listed, each of which result in the grabbing and storing of added actions and filters. Not all of these are necessarily triggered. It is up to the apply_filters and do_action functions to determine which of the referenced functions will be fired.

The $wp_action Array

The $wp_actions array holds all of the current actions invoked by do_action events in the files that are processed when a given page is loaded. Like the $wp_filter array, the contents of this array obviously depend on the page to which a user navigates.

Here is a snapshot of what is generated in the $wp_actions array just by navigating to the homepage in my particular setup.

But read on as knowing about these two arrays is only one aspect to fully understanding the underlying processes, in figuring out the entire puzzle.

Populating the Arrays, Firing the Hooks

Here’s another piece to this complex puzzle. We know that the array $wp_filter holds an array listing all of the currently active action functions and filter functions. But how is this array built?

It’s simple. All action and filter functions that are not enclosed within a function, a loop, or any type of conditional clause currently not triggered, are added sequentially to this array as a given file is executed after it’s loaded (via either an include, include_only, require, or require_only function call). Therefore, as soon as a file is loaded, execution passes to that file and all directly executable add_action, add_filter, remove_action, and remove_filter function calls are processed.

This means that PHP is furiously processing function calls from these four functions, resulting in data being added or removed from the $wp_filter array. When an add_action call is triggered, the parameters are sent to the add_action function in the WP plugin API. When an add_filter call is triggered, the parameters are sent to the add_filter function—and so on.

However, one additional function is called when an add_action call is processed. As soon as the add_action function gets called, it immediately passes on the responsibility to the add_filter function. This means that WordPress looks at action functions and filter functions as the same. This is another key insight and is why both action functions and filter functions are referenced within the same array— the $wp_filter array.

Once the add_filter function gets control, it adds the calling function to the growing list of actions and filters that can be triggered by a given do_action or apply_filters event. This process quickly results in the $wp_filter array growing into a massive, multidimensional array. Of course, action and filter functions can get removed from the array via calls from the remove_action and remove_filter functions.

The reality of code execution is of course more complex. The $wp_filter array is still being populated with action and filter functions when the first do_action events are triggered. This means that it is possible to have a situation where an action or filter that is hooked to a given do_action or apply_filters event will not get triggered if the file in which the hooked function is located has not been loaded before the hook is triggered.

This last point is exactly what was happening in BuddyPress when the bp_init action hook fired. This is the issue that was puzzling me and resulted in this exhaustive study and creation of my new WordPress Hook Sniffer plugin. You can read this BuddyPress Trac ticket to learn more.

A Detailed Analysis to Shed Some Light

Here is a breakdown and partial analysis of the $wp_actions array, the array that holds all of the current actions invoked by do_action events in the files that are processed when the homepage is loaded. We will use this array along with the $wp_filter array to figure out what is really going on.

The contents of this array obviously depends on the page to which a user navigates. This is just what happens when a non-logged-in user visits the homepage of the default BuddyPress theme in my WPMU setup. The only other plugin that is activated is my BuddyPress Privacy Component. For these tests, I am running WPMU 2.9.2 and BuddyPress 1.2.3.

NOTE: To fully understand what is going on, you need to make sure that you are looking at the completed arrays and not the partial arrays grabbed partway through page-load.

Let’s look at the order in which do_action events will be triggered. We will analyze what is happening in the first four elements of the $wp_actions array (index value of “0” through “3”). How is each action triggered and what are the results? This will start off as a detailed look into each hook’s actions, but will provide fewer details with each additional event as the basic processes become evident.

The First Four Triggered Action Events

[0] => muplugins_loaded

[3] => bp_setup_root_components


[0] => muplugins_loaded

When a user navigates to the homepage of a default BuddyPress install running on top of WPMU, the first action hook that is invoked is muplugins_loaded. This is directly triggered on line 547 in wp-settings.php. Any added actions that are tied to this event will next be triggered.

Looking at the $wp_filter array, you will see that there are no actions tied to this hook. This means that there is no subarray element with a key name of muplugins_loaded. In other words, you will not find any reference to that action event within the $wp_filter array. So, this action event does not result in any action functions getting fired.

NOTE: A triggered hook may or may not have actions tied to it. If no actions are tied to the hook, the do_action routine passes by that hook, checking the next invoked hook for added action functions to fire.

Before the next action event is triggered, something important happens.

Execution of the wp-settings.php file continues. On line 703 of wp-settings.php, all the active plugins are loaded—both blog specific plugins and site-wide plugins.

If you look at that line, $current_plugins can be modified by any added filters. That is what happens. On line 2348 of wpmu-functions.php, an add_filter call triggers function mu_filter_plugins_list. This filter modifies the contents of $current_plugins, adding any MU plugins that have been activated site wide. Processing is returned wp-settings.php, resulting in the main file of each activated plugin getting loaded.

There is an interesting item to notice within function mu_filter_plugins_list. On line 2345 of that function, the two arrays $active_plugins and $active_sitewide_plugins are merged and the resultant new array is sorted.

What does this mean? It means that when it comes to the issue of action and filter sequence firing, it does not matter which plugins you activate first. The order in which plugins are added to each of the serialized objects active_plugins and active_sitewide_plugins is immaterial. The sort function will alphabetically reorder the contents of the merged array.

NOTE: Each WPMU blog has it’s own listing of active plugins that are stored in a serialized object in the blog’s wp_x_options table. Look for the entry “active_plugins” within the option_name field of that table. The corresponding active plugins are in the option_value field of that record. All plugins that are to be activated site wide within WPMU are stored in a serialized object in the wp_sitemeta table. Look for the entry “active_sitewide_plugins” within the meta_key field of that table and the corresponding plugins that are to be activated site wide in the meta_value field of that record.

So, in our particular case with two site-wide plugins installed and activated (buddypress and bp-authz), the order in which they were activated is immaterial in determining which file is included (loaded) first by the conditional loop code starting on line 704 of wp-settings.php.

If you look in the wp_sitemeta table for the meta_key “active_sitewide_plugins”, you will see this:

a:2:{s:24:"buddypress/bp-loader.php";i:1270239897;s:28:"bp-authz/bp-authz-loader.php";i:1270396554;}

BuddyPress appears first because I activated it first—as is necessary. But, when the references to these two main plugin files are processed through the mu_filter_plugins_list function, they get sorted. This results in bp-authz-loader.php getting loaded before bp-loader.php.

This could be a big issue as all BP-dependent plugins rely on BuddyPress to be installed, activated, and loaded. Any BP-dependent plugin that comes alphabetically before “buddypress” will have their main file loaded before BuddyPress’ main file.

Barb 1: As a BuddyPress plugin developer, this is the first major insight, the first important barb that can prevent your code from hitting a snag with regards to action and filter execution.

Fortunately, there is an easy way to prevent this barb from snagging you and those that use your plugin. Make sure that BuddyPress is active before your plugin loads its core files.

Since that is exactly what I’ve done with my BuddyPress Privacy Component, there are no issues and execution quickly passes back to the loop and the next file in the $current_plugins array is loaded. This is the main BuddyPress file, bp-loader.php.

[1] => bp_core_loaded

Execution of bp-loader.php begins. On line 22 of bp-loader.php, the first custom BuddyPress action event is invoked:

do_action( 'bp_core_loaded' );

It is directly invoked, directly triggered. It is not enclosed within a function, a loop, or any type of conditional clause. This invoked event is what appears in the second element of the $wp_actions array.

Since there are currently no tied-in actions to this particular action event (as can be easily determined by looking at the $wp_filter array), the invocation of this action does not result in further actions being triggered.

The execution of bp-loader.php continues. Right after line 22, a series of conditional clauses include (load) all enabled BuddyPress modules—activity, blogs, forums, friends, groups, messages, xprofile.

As each of these files are included (loaded), any directly invoked (directly triggered) action events within each of them will also be invoked. Since there are no additional, directly invokable do_action calls within any of these files, execution is passed back to wp-settings.php.

[2] =>plugins_loaded

On line 735 in wp-settings.php, the do_action event for plugins_loaded is directly triggered.

do_action('plugins_loaded');

This is when things really start to accelerate. Up until this time, only a few lines of php code within BuddyPress have actually been run.

With the invocation of the plugins_loaded event, we now have our first action hook that has actions tied to it. Understanding what happens next leads us to the second major insight, the second important barb.

To understand what happens next, we need to inspect the elements within the plugins_loaded array of the $wp_filter array. I have extracted just that subarray element below:

plugins_loaded:
Array
(
[0] => Array
(

)


This array element is itself a multidimensional nested array. In fact, the first element (with an index value of “0”) has two action functions referenced.

An important point: each subarray of the $wp_filter array is a numeric array. Read that again. This means that the second level of the nested $wp_filter array contains numeric arrays.

You might be wondering how the index values for these numeric arrays are set. This is simple.

The key, the index value, of each 2nd-level array element is determined by the priority assigned to the event in the add_action and add_filter call. Thus, the priority set for a given action or filter function becomes the key of each element in a given hook’s multidimensional array. If a priority is not set for a given add_action or add_filter call, it is automatically defaulted to “10”. This means that any and all added actions or filters that do not specify a priority are automatically assigned to the proper action array element with an index value of “10”.

As an example, if the priority for a given added action is set to “16”, then that particular action function will be located in the array element for that action with an index value of “16”. Multiple action functions can be added under the same index value, creating an array of action functions associated with the same numeric key element. The order in which they appear is determined by the order in which they were executed.

Barb 2: This is the second major insight, the second important barb that can prevent your code from hitting a snag with regards to action and filter execution.

Now, the next piece of the puzzle is this. The order in which action functions are added to a given action array element is determined by the order in which they are encountered, the order in which their corresponding add_action or add_filter calls were fired. As we will see below, this is what makes determining the firing order of added actions and filters difficult.

Barb 3: This is the third major insight, the third important barb that can prevent your code from hitting a snag with regards to action and filter execution.

Barb 4: The higher the index key, the later the action or filter functions within that index-key grouping will get fired. Therefore, using the example above, if we set a priority of “16” for a given action function, it would get fired only after all the other action functions with a lower priority have been fired.

We have now reached the final piece of the puzzle!

Near the beginning of this article, the complexity of the do loops within the do_action and apply_filters functions was briefly mentioned. And it is within those loops that this story really finally gets resolved.

If you look at lines 166 (within the apply_filters function) and line 339 (within the do_action function) of the wp-includes/plugin.php file, you will find the code lines where the actual hooked functions are fired. Do you see the call_user_func_array() function call? That is a core PHP function. It is what will actually fire the next action or filter function in line, as determined by the data in the $wp_filter array.

The action of the call_user_func_array() function nested within the do loop is not as simple as it may seem. Why is this? Well, currently we are discussing the plugins_loaded action event and all of the tied into functions that get fired.

Look at the next action event to get triggered within the $wp_actions array. It is the action event bp_setup_root_components. But wait. Why is there another action event being triggered? We have not yet finished iterating through all of the added action functions to the plugins_loaded action event.

Once again, the reason is simple. Triggered action functions can themselves have action events. Inspecting the plugins_loaded subarray in the $wp_filter array, we see that the bp_setup_root_components action function is invoked by the plugins_loaded event via an added action call on line 2021 in bp-core.php. Within that action function there is an action event called bp_setup_root_components.

So, the sequential processing of all the added action functions with the plugins_loaded subarray of the $wp_filter function has come across a new action event to trigger. It now gets priority and further processing of the plugins_loaded subarray is put on hold until the bp_setup_root_components action event is finished processing its added action functions.

Barb 5: This can quickly result in a nested grouping of action events with the firing of their corresponding action functions. This is the final piece to the puzzle and the last and final barb that can prevent your code from hitting a snag with regards to action and filter execution.

As you are reading this, the juxtaposed actions of the do loop with the call_user_func_array() function more than likely seem obvious. It may seem this is not unexpected behavior or difficult to understand.

Whereas that is the case when all of the data is clearly laid out before you, the complex actions of these intertwined functions are not apparent when you are coding a plugin. There is no practical way to peek inside this action-event, action-function feedback loop.

This is were the true value of the WordPress Hook Sniffer plugin is revealed.

[3] => bp_setup_root_components

Here’s where we understand the last piece to this confusing puzzle.

Inspecting the $wp_filter array for this action event you will see that there are four action functions that are hooked to this action event: bp_activity_setup_root_component, bp_blogs_setup_root_component, bp_forums_setup_root_component, groups_setup_root_component.

These action functions are fired in that sequence. Since they do not have any action events which they trigger, control is passed back to the plugins_loaded event and the next action function in the plugins_loaded subarray is fired.

Applying the Lessons

When interpreting the results of the WoodPress Hook Sniffer plugin, you need to look at the output of the $wp_actions array and then search out the hooked actions to each of those items (if any) in the $wp_filter array. This will give you a general idea of what gets fired when. You can then experiment and see how changes to action priorities affect the firing sequence of a given added action.

You need to carefully think about the execution timing of each action or filter you add, looking at the corresponding triggering event for the hook or hooks to which it’s tied. Remember, you can hook a function to more than one hook which means that it is possible, if you are not careful, that some of them may fire whereas others may not. It’s all a matter of whether or not the reference to the action or filter function was successfully added to the $wp_filter array before the associated hook is triggered.

Looking at the Action Event Firing Sequence and the Filter Event Firing Sequence will help you precisely tune your added hooks and filters. Remember that execution my temporarily pass to another action or filter event. The output of these two WordPress Hook Sniffer arrays will show you when that happens.

Finally, there is no requirement that you place your add_action and add_filter calls right below the functions in which they are associated. Whereas doing so does facilitate code understanding, you could instead place them all at the top of the file (or the bottom) in which the associated functions are located. Remember, each add_action and add_filter function call that is directly executable is processed as soon as a file is loaded. So it does not matter where within the file those calls are located—with the possible exception of fine tuning the execution order of a particular function.

Final Notes on the $wp_filter and $wp_actions Arrays

The arrays $wp_filter and $wp_actions are repopulated from scratch each time a page is loaded. They do not contain a running accounting of all action and filter functions and all action and filter hooks. The contents of both of these arrays may vary depending on which page you navigate. The contents will depend on the files that are loaded (via include, include_only, require, require_only) when a given page you are on is displayed.

The reality is that, when visiting a given page, there will always be more hooks, action, and filter functions buried deep inside non-loaded files or within function blocks that are not directly hooked. The first is a result of the add_action, remove_action, add_filter, or remove_filter calls not getting fired until that file is loaded. At file load, any directly-executable do_action or apply_filters will be triggered as well. The second is the result of functions that have hooks that only get triggered if the file is loaded and the function is fired.

Although the WP Hook Sniffer will locate all action and filter hooks, and action and filter functions no mater the source–core files, custom themes, or 3rd-party plugins–what is captured depends on one simple rule—that the hooks and function calls are actually fired during page load.

As an example, WP Hook Sniffer cannot locate add_action calls that get fired on a different page than the currently loaded page. It can also not locate add_action calls that are buried inside a function that does not get triggered unless a special criteria is met. To sniff out those added actions, you have to navigate to that page so that those calls get fired or cause the special criteria to be met so that the function containing the buried action call is triggered.

Remember, the way that the WordPress Plugin API processes added and removed actions and filters is by storing (or deleting) a reference to them in the $wp_filter array. But that only happens for hooked functions that are actually encountered during page load. The $wp_filter array is wiped clean with each page load and rebuilt from scratch. The same holds true for the $wp_actions array and the action hooks it tracks.

Therefore, if you have action or filter functions that are supposed to be fired on a given page but you are not seeing that they’ve been fired, then that indicates that they are hooked to an action or filter event that finishes firing before the file in which the target action or filter functions are located even gets loaded. This is exactly what happened to me and caused me to write WP Hook Sniffer.

Summary of Barbs: the Key Insights

1. When it comes to the issue of action function and filter function sequence firing, it does not matter which plugins you activate first.

2. The key, the index value, of each 2nd-level array element within the $wp_filter array is determined by the priority assigned to the event in the add_action and add_filter call.

3. The order in which action functions and filter functions are added to a given action or filter subarray element in the $wp_filter array is determined by the order in which they are encountered during code execution.

4. The higher the index key, the later the action or filter functions within that index-key grouping will get fired.

5. Action hooks (events) –> trigger action functions –> which can have additional action hooks –> which can trigger additional action functions –> until control is passed back to the the originally-triggering action hook.

This is the action-event, action-function feedback loop caused by the juxtaposed actions of the do loop with the call_user_func_array() function.

It is interesting how some people quickly jumped to conclusions and made sweeping assumptions based on a single blog article, or worse yet, blog title. Although the majority of people who have taken the time to comment or tweet about this post have been positive about my efforts, a small minority (across the age spectrum), have been negative, even seemingly offended.

I’ve concluded that this latter group must not have read the post in its entirety. In fact, it is very possible that they got emotionally thrown-off guard by the title and didn’t bother reading the post at all. The other likely scenario is that they only read the first half of the post and found it disagreeable so they did not finish reading the rest.

Either way, it is a shame when people make accusations–are prejudiced–based on a few words. It is an unfortunate fact that some people will judged you on little more than a few words or sentences. They will not take the time to learn more about who you are before rendering an opinion.

Now I have thick skin. When you’ve been through a life-threatening illness, not sure whether you would live another year, you learn what is truly important and are able to filter out most impacts of personal attacks, illogical drivel, and emotionally-charged, incorrect assertions.

Marketing Message

Although the title of my post was somewhat sensational, it did speak directly to the issue of ageism in the VC-funding of web startups. This is a real issue.

But, my article only used that issue to build a bridge to the larger point—that what matters in startup founders in not age, but their experience, skills, and maturity. In fact, near the end of my piece I state this:

Now, I am not an ageist by any stretch of the imagination. So, if you’re an exceptional under-35 year old who is interested in this opportunity, send an email convincing me that you’re the one I should pick. You will still be required to meet all the requirements except age.

So, when it comes to my search for exceptionally-talented startup partners, this post is really not about age. I’ll gladly consider anyone, regardless of their age—although when choosing a founder, the experience-bar must be set higher.

Rash Decisions Are Not Good Decisions

The fact that someone tweeted today calling me “utterly pompous” for my statements in that article, does not surprise me nor upset me. Whenever someone sends a negative tweet about something I’ve said or written, I always engage them in respectful debate. Some will reply, a few simply ignore my tweets. My purpose is to better communicate my original message and learn what in particular set them off.

When I received that tweet this morning, I sent off three, quick tweets encouraging him to read the whole article and explaining that the major point of that piece was that I’m looking for two experienced people with the skills to be founders. I told him that it was really not about age at all.

He eventually sent another tweet back but has not yet recanted his remark. That’s fine. He’s entitled to his opinion. I have big enough shoulders. If I’m ever in need of the services his firm offers, I’ll fully assess the firm’s strengths and weakness. I will not jump to conclusions based on the little interaction that I’ve had with one of its partners.

This experience made me realize another essential quality of a great leader—to be slow to judgement. If you are too quick to judge, then you are likely a person that misses key information that could make a difference to your business’ success. You may be prone to letting emotions influence your judgement too much. Instead of making a rash assumption about a person, project, or opportunity, do your homework. Properly assess the situation so you know as much of the truth as possible before making your decision.

During the chat, Andy Peatling (lead BP developer and Automattic employee), presented an idea about breaking up development work into component teams:

I’d like to start breaking BP down into chunks, and find people that are really interested in specific features…so for example if you really love the activity stream functionality you could focus specifically on that, and stick to patching just this area…so the long term goal is to get teams on components and have that transition into core commit teams.

This has merit. As the complexity of the BuddyPress codebase expands, it will be increasingly difficult for a one- or two-person team to do all the core lifting. BuddyPress is a complex suite of plugins. It is a social-network-creating ecosystem full of hundreds of functions and classes. Breaking the workload into project teams is a sensible approach.

More Hands to Watch

But, this notion of modularizing BuddyPress core development made me realize that a single guy–that would be me–cannot effectively continue to maintain and update the BuddyPress Privacy Component. It is impractical.

As you already may know from my very successful fundraising drive for my BuddyPress Privacy Component, keeping the BP Privacy plugin up to snuff with each new release of BP is quite challenging. In effect, I have to be an expert on all the BuddyPress components.

If there will be project teams managing the future development of the BuddyPress suite of components, that means two things: 1) there will be too much information created by too many hands on which I need to stay caught up; 2.) there’s an opportunity to streamline privacy filtering.

Enter the BuddyPress Privacy API

Privacy should be a core feature of any social network. BuddyPress is no exception to this rule. So, I’m now thinking that the best approach to privacy in BuddyPress is via a Privacy Layer that provides a basic Privacy API which any and all components can access.

I’m now investigating how practical and possible it will be to create a Privacy Layer using my current privacy codebase. If it is something that can successfully be created without a significant amount of additional work, I will switch my efforts toward creating the BP Privacy Layer.

This means, that going forward, it will be up to each BuddyPress component development team to utilize the Privacy Layer (if they choose to), to tie their component into the Privacy API, and provide privacy filtering. That way, providing privacy will become a team effort and not just one guy playing catch up, running behind Andy, jjj, and all the component-team members who are furiously evolving the BuddyPress codebase.

Do you think a BuddyPress Privacy Layer is the best way to ensure that privacy becomes a core element of each component? Do you think a BuddyPress Privacy API is a desirable feature?

Since I am not hiring employees, I am not breaking anti-discrimination laws. I am not making job offers. I am searching for business partners with whom to start a business. So, I can use whatever criteria I want in selecting my startup partners.

In the days that followed that post, Dave brought up more issues of ageism—in particular venture funding in the realm of tech startups. On Wednesday, January 13, 2009, Dave tweeted this quote, taken from an article about Douglas Leone, a partner at Sequoia Capital:

“Sequoia focuses on younger entrepreneurs because people over 30 aren’t innovative.” http://r2.ly/red7

Wow! I guess Pablo Picasso, Richard Feynman, Steve Jobs, James Cameron, and hundreds of thousand of other post-30 innovators, never realized that their creativity and innovative spirits had dried up once they hit 30. Shame on them. They all should have been sent to the Soylent Corporation’s processing plant once they hit 30-years old.

If you read the article linked to in the tweet, you’ll get the full picture of what was being said. But the point is, that when it comes to web startups, especially those in the social media space, ageism is an issue.

( N.B. If you have made it this far in the article and your blood is beginning to boil, read this newer post for a sneak peek at the message behind the headline.)

Fifty is the New Forty; Thirty is the New Twenty

So, why am I looking for founding partners 35-plus years of age?

In my two previous jobs, I managed teams of people; I managed managers who managed teams of people. It was a rare exception when I found someone under the age of 30 who was sufficiently focused, task-oriented, dependable, experienced, and knew what they wanted. When I did find someone like that, I knew that I had a potential project manager and someone who might be able to be mentored to become a possible future executive.

Now that does not imply that most people over the age of 30 have what it takes to manage projects, to lead a team of people, to start a company. Most of them do not. It is simply that my empirical evidence convinced me, when it came to a professional life, most people under the age of 30 still had some growing up to do—and some of those had a long ways to go.

All under-30, professional-level employees have fewer than 10 years of work experience. Most are still very green and have much to learn about work ethos, teamwork, project management, and leadership. The other big issue is that many under-30 employees have yet to perfect an effective, proactive communication style. Finally, experience comes with discipline, hard work, learning from mistakes, and age. And experience is more valuable than raw, young talent in my book.

Don’t get me wrong. Young employees are important to a healthy, vibrant business. But a company full of only young employees is a company that is most likely inefficient and prone at making mistakes that a business with a diverse, well-seasoned workforce would never make. This applies to old firms as well as new startups.

The Company, The Opportunity

My startup is in the Publishing 2.0 space. That is all I will say for now.

I have an detailed concept paper describing the underlying vision and functionality. It is not a business plan. At this stage in a startup’s life, business plans are not necessary. If you don’t understand that statement, or understand why, then this opportunity is not for you.

You must know the differences between working at a startup and working for a small business. Whereas all startups are (usually) considered small businesses, very few small businesses are startups. If you do not clearly understand the differences, then this opportunity is not for you.

Each founder is required to provide their own hardware and software. As we will be using a number of Open Source tools for designing, coding, implementing, managing, and running the platform, the need for proprietary software should be limited.

The earliest stages of this startup will be self-funded. It should not require much initial infusion of capital beyond what is needed for hosting and membership in a few select collaborative services. I plan to run a very lean startup. The mid-term goal is to bootstrap the startup, thereby not requiring any angel or venture funding. However, I am not opposed to either if it makes sense down the road.

As this is a startup with zero outside investment and will initially have zero cash flow, founders will not receive any salary or benefits at first. You must be able to meet adequately your personal financial responsibilities and have a sufficient savings cushion to live in this way for at least 6 to 12 months. If that is not possible, if that concerns you, then this opportunity is not for you.

Founders will be owners of the company. Percent ownership will be negotiated with me on an individual basis. Stock options will also be made available.

Our company will strive to determine as quickly as possible the right fit of functionality and service for our intended target demographic. We will do this through analyzing metrics and customer development data obtained over a series of incremental launches (iterations of our platform). The initial goal will be to get a minimally viable service built as quickly as possible so that we can begin this process. We’ll then scale up our platform and service, leveraging our learned intelligence.

What I’m Seeking

In particular, I’m looking to create an energetic team that will function as generalist. We will build the initial, working technology platform, and create the business foundation.

Whereas each member of our team will have a specific, unique skill set that complements the overall startup process, there will be necessary overlap in the area of coding knowledge. This means that each team member must have sufficient Web coding experience, although only one of us truly needs to be an expert-level developer.

In the earliest stages of a Web-based startup, generalists often perform better than specialists. But, as we begin to successfully acquire members and bootstrap the business, we will hire (additional) specialists.

Here are the basic requirements (not listed in any particular order of importance):

Required of all Founders

• Must be 35-plus years of age
• High energy, positive personality
• A killer work ethic (days will be long)
• Ability to work independently
• Adept at creative problem solving
• Proven creative, innovative, independent thinking
• Ability to work initially for zero salary or benefits (this could last 6 or more months)
• Sufficient comfort level with back-end PHP coding and front-end design
• Project management experience
• Must live in the contiguous United States—for travel purposes
• Must be a citizen of the United States—for legal purposes
• Must have a computer with a video camera and high-speed Internet access
• Thrive in taking measured risks
• A healthy savings from which you can survive off of for at least 12 months
• Respectful, proactive communication style
• Easy to communicate with and a good, active listener
• Understanding that there are no guarantees of success
• Must be willing to travel to meet in person a few times in the first 6 months
• You cannot be in arrears with local, state, or federal tax institutions
• You cannot be a defendant in any pending or active lawsuit
• Founders will share corporate risk and liability
• Founders will sign shareholders’ agreement
• Must be results-oriented, focused, tenacious, and driven

More Specific Requirements—Coder, lead-developer

• At least one coder with significant experience in OOP MVC Python-based frameworks (PHP considered as well)
• Experience and knowledge of DB design theory and practice—ERDs, normalization, sharding, etc.
• Experience with PostgreSQL
• Experience with Web security
• Experience with agile development

More Specific Requirements—Designer

• CSS and HTML guru
• Ability to resolve browser-specific rendering issues
• Keen eye for clean, uncluttered, Web-2.0 style design
• A stickler for designs that validate
• User-friendly UI/UX maven

Not Required but a Plus (one or more)

• Previous startup experience as a founder
• Previous early-stage startup experience as an employee
• Extensive, high-level contacts in the New York book publishing Industry
• Understanding of Semantic Web and experience with semantic technologies
• Past P&L responsibility
• Previous position as CTO
• Law or MBA degree
• You are a Mac person

Not An Issue

• Married/unmarried with kids
• Desire not to relocate
• Desire to get some sleep each night
• It’s okay if you’re a PC person

I spent years in the PC world designing custom database solutions for big companies, I now prefer Macs. In fact, I have three Macs that I use for development. I no longer own a PC—which I have found to be a nice relief.

Now, I am not an ageist by any stretch of the imagination. So, if you’re an exceptional under-35 year old who is interested in this opportunity, send an email convincing me that you’re the one I should pick. You will still be required to meet all the requirements except age.

If Interested, Here’s What you Need to Know and Do

If you are not a highly-motivated, creative, driven, risk-tolerant, tenacious, tireless worker, then this opportunity is not for you.

This is not a job posting. It is a potential opportunity to become a startup founder.

If you are interested in being considered for a slot as one of three founders, ping me here no later than February 6, 2009.

In the body of your (brief) email tell me why this opportunity intrigues you and what experience and skills you bring to the table. Please include a link to your “About Me” page on your website (I prefer that over a digital resume). Include your Twitter and LinkedIn usernames. Finally, include your Skype or iChat contact details so that, if I think it desirable, we can have a video conference.

I will seriously review each potential candidate and make a short list of those with whom I wish to have a video conference. I retain the right to make the final decision on selection of partners. I do not guarantee that I will select any of the candidates who apply. I will not add another founder until I’ve found the right fit.

I think it is not only fair and appropriate, but also necessary for plugin developers to have the opportunity to make a living, or at least part of their living, writing great code that extends the base functionality of the BuddyPress platform.

To be clear, I am not an employee of Automattic. Like the vast majority of BuddyPress developers, I do not get paid a single cent for my contributions. In fact, as a salaried employee of Automattic, Andy Peatling, the lead developer of BuddyPress, is the only one who gets paid for his time working on this Open Source project (as far as I know).

Again, I am not looking to fan the embers of previous debates. I do not have any issue with how Automattic runs the WP plugin repository or care if they never list commercial plugins. That is not my point.

All I’m asking is how can plugin developers exist on an equal footing with theme designers when it comes to the issue of earning a living? Currently, the only three options that developers have, it seems, are to advertise a donate button for each plugin, accept consulting gigs, or accept advertising on their website. But donate buttons rarely provide much support and providing consulting services to clients is not for everyone. Furthermore, for me, I do not care to turn my personal website into a billboard.

The argument that plugin developers benefit by offering their work for free is flawed. It assumes that all developers are looking for consulting work, and two that all developers who offer their work for free will receive consulting work. Whereas it is certainly the case that some plugin developers have built a nice consulting business as a result of their donated work in the WordPress community, that does not mean that this route is for everyone.

What if a developer just wishes to code great-quality plugins like a theme designer designs high-quality themes? What if he or she does not want to provide any other service? How should this developer be compensated for their time?

But, since you asked, I do have a donate-like button for my BuddyPress Privacy Component. You can read more about my version of “donate” here.

I would like to hear some ideas on this topic as I have contributed much time to the BuddyPress community but have not earned a single penny. I am not looking to provide programming services or start a consulting company. I have a significant project that I’m working on so I don’t have time for much else.

Since I am not yet making an money on my project, I need a vehicle to earn some semblance of a respectable cash flow. Just as some theme designers earn a decent income from their premium themes, I would like to think that my income vehicle could be BuddyPress component development.

So, ideas and civil discussion, please!