WordPress Plugin Actions

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Post

Category
Code

Published Sunday May 13, 2007 at 6:00 am
By Ronald Huereca

WordPress Plugin Actions

How To Write a WordPress Plugin Series

This post was written as part of the How to Write a WordPress Plugin series.

WordPress actions allow you as a plugin author to be able to hook into the WordPress application and execute a piece of code. An example of an action would be that you want a execute some code after a user has published a post or left a comment.

Some of the actions that I use heavily are:

admin_menu: Allows you to set up an admin panel for your plugin.
wp_head: Allows you to insert code into the <head> tag of a blog

Actions in Action

While defining the structure of a WordPress plugin, I left a place holder for some actions. In this example, we are going to set up a piece of code that will run inside the <head> tag of a WordPress blog.

First we need to add a function into our DevloungePluginSeries class.

PLAIN TEXT

PHP:

function addHeaderCode() {
?>
<?php
}

All the above function does is output an HTML comment. Rather simple, but you could output just about anything. To call this function, we add an action.

PLAIN TEXT

PHP:

//Actions and Filters
if (isset($dl_pluginSeries)) {
//Actions
add_action('wp_head', array(&$dl_pluginSeries, 'addHeaderCode'), 1);
//Filters
}

From the WordPress Plugin API page, the add_action structure is as follows:
add_action ( 'hook_name', 'your_function_name', [priority], [accepted_args] );

Since we are calling a function inside of a class, we pass the action an array with a reference to our class variable (dl_pluginSeries) and the function name we wish to call (addHeaderCode). We have given our plugin a priority level of 1, with lower numbers executed first.

Running the Code

If the Devlounge Plugin Series plugin is activated, the comment of "Devlounge was here" should show up when you go to View->Source in your web browser when looking at your main blog site.

Removing Actions

If your plugin dynamically adds actions, you can dynamically remove actions as well with the remove_actions function. The structure is as follows:
remove_action('action_hook','action_function').

Conclusion

Hopefully this post gave you some insight into what you could do when hooking into WordPress actions. Once again, you can download the code for the sample Devlounge Plugin Series for actions.

Download the Code Used In This Post

For further reading, please check out these links: