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About pluggable functions

From: WordPress: Creating Custom Widgets and Plugins with PHP

Video: About pluggable functions

Pluggable functions are set of functions built into WordPress. These functions can do anything from getting the current user's information to generating hashes from strings to setting cookies. As a WordPress developer, you can use these in your plugins. All of the pluggable functions are included in wp-includes/pluggable.php. You can also find a list of them online at the Codex. If you look in the code--this is that WordPress track that's available online directly from the Codex site-- you can see before every function declaration there is a special if statement that looks to see if that function already exists or not.

About pluggable functions

Pluggable functions are set of functions built into WordPress. These functions can do anything from getting the current user's information to generating hashes from strings to setting cookies. As a WordPress developer, you can use these in your plugins. All of the pluggable functions are included in wp-includes/pluggable.php. You can also find a list of them online at the Codex. If you look in the code--this is that WordPress track that's available online directly from the Codex site-- you can see before every function declaration there is a special if statement that looks to see if that function already exists or not.

If the function doesn't exist, it then declares it. If it does exist, it then ignores the declaration. This is precisely what makes these pluggable. What that means is these are functions that are used throughout the environment of WordPress that you have the ability to override and create your own versions of. If you create your own version, these will then exist, and it will not then declare its internal version--thus pluggable. Take, for example, the plugin that we worked on. We had a function called Cc Mail.

Cc Mail uses the PHP mail function to send out the mail. Well, let's say we want to send it through a universal mail application that was used within WordPress. There is one called wp mail, and if you click on it in the Codex, you'll see the format is very similar to PHP mail-- only we have the ability to override this. So maybe it's something we want to utilize. To change it, you simply use the function, because it's already included in the WordPress environment. WordPress has a set of built-in functions called pluggable functions.

These can be helpful when we need to use them. Simply find them in the pluggable PHP file, or here in WordPress Codex. They provide us with some special functionality that is not available everywhere within WordPress. What makes them pluggable is the ability to override them if we want to, and that new functionality will be used all throughout the WordPress environment.

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This video is part of

Image for WordPress: Creating Custom Widgets and Plugins with PHP
 
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  1. 1m 49s
    1. Welcome
      1m 16s
    2. Using the exercise files
      33s
  2. 23m 29s
    1. WordPress overview
      2m 32s
    2. Installing WPI for Windows
      3m 42s
    3. Installing MAMP for the Mac
      3m 25s
    4. Installing and configuring WordPress
      5m 51s
    5. Comparing WordPress 3.0 with previous versions
      2m 57s
    6. Setting up a PHP/WordPress development environment
      5m 2s
  3. 14m 47s
    1. Exploring WordPress plugins
      3m 42s
    2. Administering plugins from the WordPress admin
      5m 23s
    3. Exploring where plugins reside
      2m 51s
    4. Introduction to hooks
      2m 51s
  4. 39m 28s
    1. Creating the plugin PHP file(s)
      3m 12s
    2. More on hooks: Actions and filters
      3m 15s
    3. Installation and activation
      4m 6s
    4. Writing activation code
      3m 45s
    5. Writing an action
      5m 12s
    6. Writing a filter
      4m 15s
    7. About pluggable functions
      2m 1s
    8. Writing a pluggable function
      5m 30s
    9. Using template tags
      2m 46s
    10. Introducing shortcode
      5m 26s
  5. 26m 2s
    1. Widgets and the WordPress Widgets SubPanel
      2m 54s
    2. Comparing widgets and plugins
      1m 8s
    3. Using and customizing built-in widgets
      3m 18s
    4. Creating a new widget
      7m 21s
    5. Writing the constructor and registering widgets
      5m 20s
    6. Enabling configuration of widgets
      6m 1s
  6. 44m 59s
    1. Creating an admin interface
      5m 25s
    2. Saving data to the database
      5m 39s
    3. Securing form submission with nonces
      2m 25s
    4. Options editing post-WordPress 2.7
      4m 8s
    5. Integrating with the WordPress admin menus
      3m 34s
    6. WordPress admin dashboard API
      4m 5s
    7. Using existing options and option editing pages in WordPress
      5m 19s
    8. Using jQuery and AJAX for administration
      14m 24s
  7. 27m 13s
    1. Accessing the WordPress database
      5m 45s
    2. Using the built-in schema
      2m 21s
    3. Accessing data using $wpdb
      5m 15s
    4. Creating new tables
      7m 18s
    5. Inserting data
      6m 34s
  8. 26m 27s
    1. Introducing the Loop
      6m 22s
    2. Using WP_Query()
      3m 11s
    3. Custom filtering and sticky posts
      4m 58s
    4. Using jQuery and AJAX for posts and pages
      11m 56s
  9. 12m 9s
    1. Registering and promoting plugins
      2m 28s
    2. Creating an uninstall function
      5m 53s
    3. Backward compatibility issues
      3m 48s
  10. 15m 3s
    1. Understanding security issues
      11m 20s
    2. Internationalizing your plugin
      3m 43s
  11. 18s
    1. Goodbye
      18s

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