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Creating a new widget

From: WordPress: Creating Custom Widgets and Plugins with PHP

Video: Creating a new widget

Building a WordPress widget is pretty much the process of building a plugin, but we use some special techniques to do it. Everything is going to happen in a single file using the WordPress Widget API. As long as you know the basic framework, everything will fall right into place. You need to code your widget using three major functions: Widget, Update, and Form. In this unit, we are going to discuss generating the widget interface using widget and registering the widget. So let's to into PDT eclipse, and you can see I have created a new file called simpleWidget, and I have put all my comments in it, just like I would have with any other plugin.

Creating a new widget

Building a WordPress widget is pretty much the process of building a plugin, but we use some special techniques to do it. Everything is going to happen in a single file using the WordPress Widget API. As long as you know the basic framework, everything will fall right into place. You need to code your widget using three major functions: Widget, Update, and Form. In this unit, we are going to discuss generating the widget interface using widget and registering the widget. So let's to into PDT eclipse, and you can see I have created a new file called simpleWidget, and I have put all my comments in it, just like I would have with any other plugin.

Since WordPress 2.8, they added an object- oriented methodology for creating widgets. There is another way to do it, and you can see it online in the main Widgets page in the Codex. There's a special section about creating widgets before 2.8, and this is a fine way to do it; however, creating it the object- oriented way is a lot cleaner and neater, and is considered the best practice. So the way to do this is we actually create a class file. So creating classes in PHP is a matter of declaring the name of your class, giving it a name--in this case, we will call it SimpleWidget--and if it's going to extend any specific class, that is, if it's going to inherent things from another class, then you need to define it by saying extends, and then in this case, there's a special class called WP_Widget, which is made specifically for creating widgets.

So this is a basic class definition, and you can write other plugins using classes as well. However, in this case we are just going to do it for the widget. Every class has a basic function called the constructor, and this is a class that's called when you create a new instance of this class. So we are going to declare ours as SimpleWidget. Notice that it matches exactly the name of the class. Then we need to declare three special functions, and these are what make widgets work. The first function is widget.

The widget function is going to output the user interface. We also have an update function, which will be used for handling any update functionality, and finally a form function, which will be used if we have any configuration options. Once you have all these declared, the next main step is going to be to create the actual user interface using the widget function. So this function is going to take two arguments.

The first one is called args, which are basically going to be the arguments from the theme. So this function is going to get called internally whenever a widget is pulled into the user interface, and when it calls it, it's going to pass to it the arguments from the theme which allow us to get some specific information from that theme, like all of the HTML that comes before the widget, all HTML that comes after it, the title and some other information. So we declare that, and then we declare an instance.

An instance is going to give us essentially an instance of the class. In here, the first thing we want to do, to make our lives easier we can use a special function called extract. Extract will take whatever you pass it as an object, it will parse it out, and it will then put it into variables that you can use in your function so that we don't always have to use the prefix. So we are going to essentially take all the args out and make them local variables, and we are going to use this EXTR_SKIP constant.

We are going to pass to it as well. That will essentially protect any existing variables. Now we can set our title equal to, and this is a funny little bit of code. So we are looking at the instance property, and we're going to see if there's a title in here. So notice how it's wrapped in parentheses. Basically what we are doing here, this is a shorthand if-else statement. So we are saying if there is something in this instance title, then we are going to set our local title variable equal to that value.

Else we are going to set it to "A simple widget." So this is essentially setting a default title. In addition, we are going to create a body and do the same basic process. Look to the instance and see if there's a body property, and if there is, then we will set the body equal to that property, and if not, the body will just some simple text.

On your example you might want to say, let's say your widget is outputting some kind of list of e-mails or something, you might want to have a default message that says, "No e-mails available," because if there's no body then that means there's obvious nothing to output. So now what we are going to do is since I am going to be writing some HTML--because this widget function is actually outputting user interface--I am going to close my PHP, and that then allows me to just write as if I'm in a regular PHP page. So I am going to echo this special variable, before_widget, and this came from our arguments, and I can access it like a local variable because I used this extract function.

Then I am going to output before the title, and I am going to append to it the title and append to it after title. So that's going to essentially output the title and then wrap it in this before_title and after_title, which is usually some form of div tag or some kind of HTML. Then I am going to write a paragraph, and inside the paragraph, I am going to echo whatever is in the body, which is going to be, of course, whatever was passed into this instance of the widget, or it's going to just put the default if nothing was set, and then once I am done, make sure to reopen the PHP, so that I can continue to parse the rest of the page.

So this is the basics of putting together a widget using WordPress's Widget API. We will talk about how to register this widget and use it in a WordPress environment later. I'll note that widgets are meant to go hand-in-hand with themes. If you want to know more information on developing themes and using themes, please refer to the lynda.com course on that topic. So overall building a widget using Widget API requires a little understanding of object-oriented programming. Because we are extending this built-in WP_Widget class, we have these functions available to us that ensure everything is created in a consistent manner.

In this unit, we use the widget method to output the widget body itself. In the next unit units, we are going to talk about how to create update and how to create forms to allow users to edit some configuration options and save those to the database.

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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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