Unfortunately, most themes don’t have support for custom menus yet.  Wordpress makes it easy to add them as widgets, but if you want real menus, they need to be enabled in your theme.

Step 1:  Enable Custom Menus

The first thing that you need to do in order to get custom menus working in WordPress 3 is enable them.  To do that, open up your theme’s functions.php file, and drop in the following code.

function register_custom_menu() {
register_nav_menu('custom_menu', __('Custom Menu'));
}
add_action('init', 'register_custom_menu');

Once you have done that, go to Appearance -> Menus and you should see something like this.

Step 2:  Add the Menu to Your Theme

Assuming that you’ve created a custom menu and want to display it, you’ll need to add the display function to your theme.  In most cases, you’ll need to open up the header.php file, and the area that looks like a menu.  This changes for every theme, but it should be fairly obvious.  Once you find it, insert the following code.

<?php wp_nav_menu(array('menu' => 'custom_menu')); ?>

After that, you’re menu should display in your navigation bar.  Good luck!

function exclude_my_plugin( $r, $url ) {

if ( 0 !== strpos( $url, 'http://api.wordpress.org/plugins/update-check' ) )
>return $r;
$plugins = unserialize( $r['body']['plugins'] );
unset( $plugins->plugins[ plugin_basename( __FILE__ ) ] );
unset( $plugins->active[ array_search( plugin_basename( __FILE__ ), $plugins->active ) ] );
$r['body']['plugins'] = serialize( $plugins );

return $r;
}
add_filter( 'http_request_args', 'exclude_my_plugin', 5, 2);

Attribute:  This code is originally from a lead WordPress Developer, Mark Jaquith (thanks Mark!)

But how does this exclude your plugin from the update?  First, it takes the HTTP Request args and unserializes the ['body']['plugins'] part of it.  From there, it’s as simple as unsetting your plugin from the array, then re-serializing the request args.  Also the first part checks to see if this is actually and update check.  If it’s not, you exit the function.

add_custom_background();

After that, under the Appearance menu you should have a “Background” option link.  When clicked, it will look like this.

From there, upload your custom background and bask in your own glory!

Note:  The full source code for this plugin can be found here.

Every time you go to WordPress blog and see items in the sidebar, it’s likely that they are widgets.  There are thousands of them for download on WordPress.org, but what if you want to create your own?  How would you code it? That’s what I will answer in this quick How-To.

<?php
/*
Plugin Name: Sweet Math Widget
Plugin URI: http://www.re-cycledair.com
Description: A math widget that takes the post id and multiplies it by 5.

Author: Jack Slingerland
Version: 0.1

Author URI: http://www.re-cycledair.com
*/
function sweetMathWidget() {

global $post;
echo "{$post->ID} x 5 = ";
echo $post->ID*5;
}
?>

function sweetMathWidgetInit() {
register_sidebar_widget(__('Sweet Math Widget'), 'sweetMathWidget');
}
add_action("plugins_loaded", "sweetMathWidgetInit");

function sweetMathWidget($args) {

global $post;
extract($args);
echo $before_widget;
echo $before_title;
echo "<h2> Sweet Math Widget </h2>";
echo $after_title;
echo "{$post->ID} x 5 = ";echo $post->ID*5;
echo $after_widget;
}

Enable

The first step to using post thumbnails in WordPress is to enable them.  To do that, all you need to do is put the following in you themes functions.php file.

add_theme_support('post-thumbnails');

Once you’ve added this code, you should see a box underneath “Post Tags” in the Edit Post screen.

Set the Post Thumbnail

Now that you have the featured image box in you WordPress Edit Post area, you need to click the “Set featured image” link.  Once you do that, you’ll be greeted with the usual WordPress image upload screen.  Select the image you would like to upload, and then let WordPress do it’s image crunching magic.  Now comes the most important part, you need need to click “Use as featured image”.

Once you’ve done that, you’ll get a thumbnail version of the photo you just uploaded in the lower-right hand corner of you Edit Posts screen.

Using Post Thumbnails in Your Theme

Obviously post thumbnails aren’t much use to you if nobody can see them.  To see them in your theme, you need to call the following function while inside The Loop.

 <? the_post_thumbnail(); ?> 

That’s it!  It’s now easier than ever you have each one of your posts have a thumbnail.  If you have any questions, please leave them in the comments.

Digg Oregon Train Error Page (click to enlarge)

Nice job leveraging Oregon Trail guys.

function content_myshortcode($content)
{

if(preg_match('/<!--myshortcode[\(]*(.*?)[\)]*-->/',$content,$matches))
{
$parameter1 = $matches[1];
$content = preg_replace('/<!--myshortcode(.*?)-->/',myshortcode(false,$parameter1), $content);
}

return $content;
}

Now what does this do?  This function will go through the content of your post/page, and look for the <!–myshortcode–> shortcode.  If it finds it, it will then call the “myshortcode()” function in your plugin and put it’s content there.  Now, this doesn’t happen automatically.  As with most WordPress development, we need to add a filter.

add_filter('the_content', 'content_wacoverages');

WPDB Queries

Let’s say that you would like to run a simple query that returns all of the rows in the “posts” table.  With the WPDB class, all you need to do is execute:

$rows = $wpdb->get_results( "SELECT * FROM $wpdb->posts" );

When this code is executed, it returns the entire table “posts” ($wpdb->posts) as an array of objects into the $rows variable.  From there, it’s easy enough to iterate over the array using a foreach loop.

WPDB Insert

Inserting data into a table is easy using the WPDB class.  All you need to know are the column name(s), the table name, and data you want to store.  I’ll lead with an example:

$wpdb->insert( 'links', array( 'link_url' => 're-cycledair.com', 'visit' => 12 ), array( '%s', '%d' ) );

This example of $wpdb->insert, inserts “re-cycledair.com” and “12″ into the link_url and visit columns of the “links” table respectively.  The third argument in this function is one that tells the WPDB what type these values are.  The first value is a string, so we use “%s”, and the second is an integer, so we use “%d”.

If you would like to know the auto-incremented id of this insert, simply call:

$wpdb->insert_id

WPDB Update

Updating rows in a table is also easy with the WPDB class. Here is an example of an update.

$wpdb->update( 'links', array( 'link_url' => 'wordpress.org'), array( 'ID' => 15), array( '%s'), array( '%d' ) )

As you can see, this works a lot like $wpdb->insert. The first argument is the table name. The second argument is an array of column-value pairs. The third argument is the where condition (if ID is equal to 15). The fourth argument tells the WPDB class that you are updating a string, and the fifth argument says the WHERE condition is an integer.

WPDB Prepare: Protect Against SQL Injection

One thing every WordPress developer needs to know about is SQL injection. SQL injection is when someone is able to modify your SQL query to execute their own. To prevent this kind of malicious attack, the WPDB class has a method called “prepare”. “Prepare” will take your input data an sanitize it, so that it cannot be used in a SQL injection attack. An example is as follows:

$wpdb->query( $wpdb->prepare( "
	INSERT INTO $wpdb->posts
	( post_id, post_content )
	VALUES ( %d, %s)",
        15, "this is un'safe" ) );

As with previous examples, the “%d” and “%s” function as placeholders for the sanitized data.

With those functions and a little bit of work, you should be writing WordPress database queries with the WPDB class in no time!