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Writing an action

From: WordPress: Creating Custom Widgets and Plugins with PHP

Video: Writing an action

Actions are the events of WordPress. That is to say when you want something of your own making to happen inside of WordPress, you are going to use an action. If you want something to happen when a menu is generated, you'll use an action. If you want something to happen when the users saves a comment, you use an action. So the process of writing plugins that do things is really a process of writing what you want done, then associating that with one of WordPress's many actions. To do that, we are going to use the add action method, which we will talk about in a second. But the first thing we need is a plugin. So I have created this file here, cc_ comment.php in my plugins directory.

Writing an action

Actions are the events of WordPress. That is to say when you want something of your own making to happen inside of WordPress, you are going to use an action. If you want something to happen when a menu is generated, you'll use an action. If you want something to happen when the users saves a comment, you use an action. So the process of writing plugins that do things is really a process of writing what you want done, then associating that with one of WordPress's many actions. To do that, we are going to use the add action method, which we will talk about in a second. But the first thing we need is a plugin. So I have created this file here, cc_ comment.php in my plugins directory.

You can see I have set up all the comment information so that WordPress administrator can read it and see it. Now I need to essentially write the function that's going to do what it is I want to be done. In this case, I am going to set it so that whenever someone submits a comment on the front-end of the web site, it's going to send a CC e-mail to some particular e-mail address. So we will create a new function. We'll call it cc_comment. And it's a good idea to create your functions with some special name. You may want to get more specific than this, so that it doesn't collide with other functions in the WordPress environment.

In the function itself, I want to have access to the _request scope. That way I can get the information that has been submitted from the form. In order to do that in my functions, I am going to declare it using the global keyword and then typing $_REQUEST. I now have access to the request scope, and I can use whatever variables I want to inside of it. The next that is to set up some variables that are going to store information that's going to be used by the e-mail. to, we can send this to drew@somewhere.com.

We will set a subject, and in the subject, we are going to say, "New comment posted @ yourblog," and of course we could use some other ways to access what their blog name is from the information, but for now we are just going to keep it simple. Then _REQUEST, and the request scope is all stored in associative array, and the name of this subject field is subject. Then I am going to set the actual message. I'm going to say, "Message from:" and note that I'm using the dot, which is just the concatenator in PHP.

So in a sense, you just append this on to my string, REQUEST, and then there's a name field which has the name of the user that they submitted. And we will say, 'at e-mail,' and then we can use a concatenator add REQUEST, e-mail. Then we can use a concatenator and add on the actual message. And I am going to add a new line, and that field is called comments.

So now I have got all my variables set up. I am going to actually do the mailing. I am going to keep it simple and use the built-in PHP mail function, and you can see the arguments it takes. The first three are the to address, the subject, and the message, and I don't need to send any additional headers or parameters. So I go ahead and just pass the fields that I have just created, to,$subject. So there we have it. That's my function. This however is never going to execute. If you remember, when I activate a plug- in, it will run any code that's not in this function, and currently, I don't have any code that's not in this function.

So what I want to do is outside of this function, I want to add this is an action. So I use the add_action method, I pass the name of the action--in this case it's called comment_post, and I know this from the WordPress Codex--and then the name of the function that I want to execute for that action: cc_comment. So that's all it takes. If I now go to my WordPress Plugins page, you can see my plugin right here. When I activate it, it will now set it up so that any future comments that are submitted will send an e-mail along with it.

If you should ever want to remove an action, you can use the remove_action, and it takes the same arguments. You specify the name of the action and then the name of the function that you want to remove. Of course, we don't want to do this because we've only just added it, but it gives you the flexibility to do that. So WordPress actions really allow us to get into WordPress and do all kinds of stuff in all kinds of places. We looked at one particular action, but there are tons of these. There are hundreds of them. The way I like to think of them is they're like power outlets around an empty house: all you need do is plug your appliances in wherever you want to, and then you can have that in that room.

There's one less thing to mention is there's a third argument here, which is priority. Priority allows you to determine what order you want these to execute in. In this case, it doesn't really matter, but in other cases it might. I recommend, to become familiar with this, is going through the Codex and looking at the plugins API, and in addition, you can check out Adam Brown's web site at adambrown.info.

Show transcript

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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