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WordPress: Creating Custom Widgets and Plugins with PHP

More on hooks: Actions and filters


From:

WordPress: Creating Custom Widgets and Plugins with PHP

with Drew Falkman

Video: More on hooks: Actions and filters

As you know, hooks are what make plugins work. There are two basic kinds of hooks: actions and filters. Each of them serve a different purpose. Actions are performing all kinds of tasks in WordPress processing. Filters are specifically for filtering text, either before it could send to a web page or before it can save to the database. We are going to talk about these hooks and how you can register and use them in your custom plugins. So first of all, filters are how we parse text. So you can see here in the plugin API at the codex.wordpress.org, there are some functions that relate specifically to filters.
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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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WordPress: Creating Custom Widgets and Plugins with PHP
3h 51m Intermediate Nov 04, 2010

Viewers: in countries Watching now:

In WordPress: Creating Custom Widgets and Plugins with PHP, Drew Falkman teaches PHP developers how to create custom functionality for WordPress 2.0 through 3.0 using widgets and plugins. This course starts by installing and setting up WordPress 3.0 on both Mac and Windows, then provides an in-depth look at tasks related to these WordPress add-ons: installing and administering, building and customizing, creating editable options and database tables, working with posts and pages, and utilizing jQuery and AJAX. There are also tutorials dedicated to promoting a widget or plugin, adding security, and localizing the interface. Exercise files are included with the course.

Topics include:
  • Installing WPI and MAMP server solutions
  • Administering WordPress plugins
  • Introducing hooks
  • Writing the PHP for a plugin
  • Using template tags and shortcode
  • Building a new widget
  • Creating an admin interface
  • Accessing the WordPress database
  • Using jQuery and AJAX for posts and pages
  • Registering and promoting plugins
Subjects:
Developer Web CMS
Software:
WordPress
Author:
Drew Falkman

More on hooks: Actions and filters

As you know, hooks are what make plugins work. There are two basic kinds of hooks: actions and filters. Each of them serve a different purpose. Actions are performing all kinds of tasks in WordPress processing. Filters are specifically for filtering text, either before it could send to a web page or before it can save to the database. We are going to talk about these hooks and how you can register and use them in your custom plugins. So first of all, filters are how we parse text. So you can see here in the plugin API at the codex.wordpress.org, there are some functions that relate specifically to filters.

The key ones are going to be has_filter, which can determine if a filter exists, add_filter which we'll used to add a new filter, and remove_filter if you ever want remove one of your existing filters. There is different categories on filters, and you can find them in the filter reference. It's in the plugin API, in a folder called Filter_Reference, and this has a list of all kinds of filters. You can see Database Reads and Writes for the Post and Page attachment, Comment and Trackbacks, Categories, Links, Date and Time, Author and User, basically all of the different places in WordPress where they are accessing some kind of textual data.

So anytime you want to make changes to a text, either before you save or before you send it to a web page, this is where you can do it. Actions on the other hand, are where we perform some specific task. When something is happening, when a comment is being submitted, or when a menu is being created, all of these things are actions. So actions function a little differently because they don't necessarily have to do with text specifically. They usually have to do with some sort of function that's going on. But the way they behave is very much the same as filters.

So the functions are quite similar; has_action will allow to determine if one exists, add_ action will allow you to essentially hook into that action, and remove_action will also allow you to remove it. Just like with filters, there is a reference at the codex under Action_Reference, in the plugin API. Again, you can see this has broken down by the different types of places where these actions occur. A typical request, you can see, there is a number of different action hooks that takes place in the request.

Wp_footer, for example, runs when the user's footer is loaded, both in the backend and in the front-end. wp_enqueue_script is what's used to generate all of your JavaScript calls, and so forth. So you'll get very familiar with these throughout the course and definitely throughout the process of filming plugins. So filters and actions are the different types of hooks that can be used in the WordPress plugin environment to perform tasks. The key thing to remember is that filters are used when you want to do something to the text, either before the text is sent to the database or the browser or wherever else, if it's going out to an iPhone or something like that.

Actions, on the other hand, are hooks that are called when something happens in WordPress: a post is saved, an admin menu has generated, the footers is being created, and all that kind of stuff. We can then create our own functions, set them to these filters and actions, and bam: we've got our plugins.

Find answers to the most frequently asked questions about WordPress: Creating Custom Widgets and Plugins with PHP.


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Q: Do I need a web hosting service for this course?
A: You don't need a hosting site to do any testing or development work that’s covered in this course. However, if you want to have your WordPress site available to the public, you will most definitely need a WordPress site. If you are hosting with an independent company, they will need to have PHP and MySQL installed, and there will be some configuration differences, but basically, you can upload anything on your local version to the web site. If you are hosting with Wordpress.com, you will need to add your plugins by uploading them manually through the WP Admin Plugin screen.
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