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WordPress: Creating Custom Widgets and Plugins with PHP
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Accessing the WordPress database


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WordPress: Creating Custom Widgets and Plugins with PHP

with Drew Falkman

Video: Accessing the WordPress database

WordPress is powered by a MySQL database. The main way that we can access this database directly is using the special wpdb class, which is loosely based on EasySQL. It's an abstraction of the SQL language for MySQL, and it does require a little bit of knowledge of Structured Query Language. Keep in mind that while you can access most of the data in the database directly, you probably don't want to do. There are a lot of different functions made there to get options and get posts and pages and things like that. You want to use those where possible.
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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

Accessing the WordPress database

WordPress is powered by a MySQL database. The main way that we can access this database directly is using the special wpdb class, which is loosely based on EasySQL. It's an abstraction of the SQL language for MySQL, and it does require a little bit of knowledge of Structured Query Language. Keep in mind that while you can access most of the data in the database directly, you probably don't want to do. There are a lot of different functions made there to get options and get posts and pages and things like that. You want to use those where possible.

Eventually, you may be creating your own database tables, and this can be helpful to know. I have a dbinfo.php plugin that I created in our plugins directory, and it's set up to be a widget in the admin. So you can see I've added this dashboard widget function which registers that function, and then I added the action. So I am all set up, just like we learned how to do in the admin widgets video. What I am going to do now is I am going to access the wpdb class, so the first thing I need to do is set it into the global scope.

That allows me to access it at will. Now I am going to output some data. First, I am put a little title, "DB Info Dashboard Widget," and under here--let's make sure to close that out because I am going to be using a PHP in here. And let's go ahead and just output this directly, so we'll just put little pre, and we'll just say php echo. And there is special function called var_dump, which allows you to see the properties of any object, and we'll just pass in $wpdb.

So we'll save it, and let's go into the Plugin screen and activate it, and then we can go to our dashboard, and we should see it up here. So you can see, it's output all this data. We have show_errors, suppressed_errors, last_error, num_queries, num_rows, rows_affected, and all kinds of different information that tell us about the database. All the different fields are available as properties. You can see I have the categories field. I have some other things, the users table, the taxonomy table--all this information I can access.

We don't need to see all that though, but maybe we do want to see a couple of things. So let's add something that will output the last query. So to do that, we simply echo $wpdb-->last_query. I am going to close the paragraph. We'll do another one that will show the last error. It's just for admin users, so they can see what's going on in the database.

Let's go ahead and refresh. So you can see we have our last query, which is something in regards to generating the menu, and the last error, which is nothing, because we haven't had any errors yet. All right, so let's go ahead and get some more information. There's a special query method that will run the query, but it'll returned how many records were affected by that query. And a lot of times we use this for insert and updates and things. But it can be a good way to get a count of something. So Total Users, and then we can just say echo $wpdb-->query and then in here, we can just say SELECT ID from wp_users.

And you can type in the fields directly, although usually you're going to want to use these variables, which I'll show you in a second. So you can see I have two users currently in the database. If you want to access data from the database, there's basically four ways you can do it: You can get a single field from the database, you can get a single column, you can get an entire row, or you can get a whole result set from a query. So if I wanted to just get a single field, I am going to ahead and get the Last post, and we are just going to say echo $wpdb-->get_var, and then I want to say SELECT post_title FROM and then to use table names that are built in, you can just concatenate on the properties, wpdb, and this is going to be in posts, dot.

And then you can add a where clause: WHERE post_author=. Let's got ahead and put this on a new line so we can read it. Make sure you have enough space in between here. Now, I want to get the ID of the current user, and I can do that by globalizing the current user property. So now I can just concatenate in here, the ID. So this will tell whoever's looking at the query the last post that they made, and then we'll close the paragraph. Refresh it.

So the last post was Hello world! which is the only post because we're just using the default installation. When you go into get an entire column, an entire row, or a result set, you are going to use Get call, Get row, or Get results. They basically work the same way where we are going to pass a query, only instead of returning a single value, they're actually going to arrays, and you can control how that's output, and we'll look at how to use those in future videos. So WordPress has the built-in wpdb class that allows us to access the built-in WordPress database.

In addition to the number of properties it has that can give you all kinds of information about the database, it also has a number of methods that allow you to query the database in a number of different ways directly.

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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