Sample WordPress Action and Filter Hooks

gistfile1.php

Code Samples for Hooks And Filters Class

<?php

/* Filter the title to add a page number if necessary.
   ------------------------------------------------------------------------------------ */

add_filter( 'wp_title', 'page_numbered_wp_title', 10, 2 );

function page_numbered_wp_title( $title, $sep ) {
	global $paged, $page;

	if ( is_feed() ) {
		return $title;
	}

	// Add a page number if necessary.
	if ( $paged >= 2 || $page >= 2 ) {
		$title = "$title $sep " . sprintf( __( 'Page %s', 'my-text-domain' ), max( $paged, $page ) );
	}

	return $title;
}

/* Force One Column Layout for WordPress Dashboard Pages
   ------------------------------------------------------------------------------------ */

add_filter( 'screen_layout_columns', 'change_to_one_columns_pages_layout' );
function change_to_one_columns_pages_layout( $columns ) {
    $columns['page'] = 1;
    return $columns;
}

add_filter( 'get_user_option_screen_layout_page', 'change_screen_layout_pages' );
function change_screen_layout_pages() {
    return 1;
}

/* Add a signature image to the end of a post
   ------------------------------------------------------------------------------------ */

add_filter( "the_content", "content_signature" );

function content_signature($content){
   if(is_single()){
      $content .= '<p><img src="'. 'http://demo.handsonwordpress.com/wp-content/uploads/2014/08/' .'author.jpeg" alt="Nicholas R. Batik" /></p>';
      return $content;
   }
}

/* Add default text to page, post, and custom post-type titles
   ------------------------------------------------------------------------------------ */

add_filter( 'default_title', 'wpatx_default_post_title', 10, 2 );

function wpatx_default_post_title( $title ) {
	global $post_type;
	switch ( $post_type ) {
		case 'post':
			$title = "Project: ";
			break;
		case 'page':
			// $title = "<p>All my Pages start with this paragraph</p>";
			break;
		case 'daily':
			// $title = "Daily Log - ".date("m/d/y");
			$title = "Daily Log - ".date("Y-m-d");
			break;
	}
	return $title;
}
	
/* Add default text to page, post, and custom post-type content
   ------------------------------------------------------------------------------------ */

add_filter( 'default_content', 'wpatx_editor_content', 10, 2 );

function wpatx_editor_content( $content, $post ) {

    switch( $post->post_type ) {
        case 'post':
			$content = "This is my default content that I want to add to the beginning of every post: ";
		break;
		case 'page':
			// $title = "<p>All my Pages start with this paragraph</p>";
        case 'sources':
            $content = 'your content';
        break;
        case 'stories':
            $content = 'your content';
        break;
        case 'pictures':
            $content = 'your content';
        break;
        default:
            $content = 'your default content';
        break;
    }

    return $content;
}

/* Change the footer to include automatically updating copyright date
   ------------------------------------------------------------------------------------ */

add_action('wp_footer', 'wpatx_footer_copyright', 100);

function wpatx_footer_copyright() {
    $backtotop_text = '';

    $copyYear = 2012; 
    $curYear = date('Y'); 

    $creds_text = 'Copyright &copy; ' . 
    	$copyYear . (($copyYear != $curYear) ? '-' . $curYear : '') . 
    	' <a href="'.site_url().'">Austin WordPress Demo Site</a>. <br />All Rights Reserved &#xb7;' .
    	' Site design and development by' .
    	' <a href="http://PleiadesWebCenter.com" target="_blank">Nick Batik</a>' .
    	' using <a href="http://wordpress.org/" target="_blank">WordPress</a>' .
    	' &#xb7;' .
    	' <a href="'.site_url().'/wp-admin">Admin</a>';

    $output = '<div class="creds">' . $creds_text . '</div>';

    echo $output;

}  

/* Replace strange text characters that are pasted into posts
   ------------------------------------------------------------------------------------ */

add_filter('the_content','filter_content_gremlins');
add_filter('the_excerpt','filter_content_gremlins');
add_filter('content_save_pre','filter_content_gremlins');

function filter_content_gremlins($content) {
	$content_gremlins = array (
	                          ' ',
	                          '“',
	                          '”',
	                          '—',
	                          '’'
	                          ); 
	$content_zapgrems = array (
	                          ' ',
	                          '"',
	                          '"',
	                          '—',
	                          '\''
	                          ); 
	$content=str_ireplace($content_gremlins,$content_zapgrems,$content);
    return $content;
}

/* Remove blog comments autolinks
   ------------------------------------------------------------------------------------ */

remove_filter('comment_text', 'make_clickable', 9);


/* Add Private Notes to Posts
   ------------------------------------------------------------------------------------ */

// How to use: add [note]<em>Your note text</em>[/note]  

function sc_note( $atts, $content = null ) {  
     if ( current_user_can( 'publish_posts' ) )  
        return '<div class="note">'.$content.'</div>';  
    return '';  
}  
add_shortcode( 'note', 'sc_note' ); 


/* Add Custom body-classes based on categories
   ------------------------------------------------------------------------------------ */

add_filter('body_class','wpatx_section_style');
function wpatx_section_style($classes) {
	global $post;
	
	// Add the page or posts taxonomy terms to the body class
	$terms = get_the_terms( $post->ID , 'category' );

	// Loop over each item since it's an array
	if ($terms) {
		foreach( $terms as $term ) {
			$classes[] = 'term-' . $term->slug;
			unset($term);
		}
		
		if (in_array('term-category-item-1', $classes)) { $classes[] = 'background-green'; }
		elseif (in_array('term-category-item-2', $classes)) { $classes[] = 'background-pink'; }
		elseif (in_array('term-category-item-3', $classes)) { $classes[] = 'background-red'; }
		elseif (in_array('term-category-item-4', $classes)) { $classes[] = 'background-teal'; }	
		else { $classes[] = 'background-red'; }
	} else {
		$classes[] = 'background-red';
	}
	
	// return the $classes array
	return $classes;
}


/* Custom Shortcode to display active hooks and filters on a WordPress page or post
   ------------------------------------------------------------------------------------ */

add_shortcode('wpatx-hook-list', 'list_hooks');

function list_hooks( $filter = false ){
	global $wp_filter;
	global $user_ID;

	// First check of user is logged in as admin
	if( $user_ID ) {
		if( current_user_can('level_10') ) {

			$hooks = $wp_filter;
			ksort( $hooks );

			foreach( $hooks as $tag => $hook ) {
				dump_hook($tag, $hook);
			}
		}
	}
}

function dump_hook( $tag, $hook ) {
	ksort($hook);

	echo "<pre>>>>>>\t<strong>$tag</strong><br>";

	foreach( $hook as $priority => $functions ) {

		echo $priority;

		foreach( $functions as $function )
		if( $function['function'] != 'list_hook_details' ) {

			echo "t";

			if( is_string( $function['function'] ) )
			echo $function['function'];

			elseif( is_string( $function['function'][0] ) )
			echo $function['function'][0] . ' -> ' . $function['function'][1];

			elseif( is_object( $function['function'][0] ) )
			echo "(object) " . get_class( $function['function'][0] ) . ' -> ' . $function['function'][1];

			else
			print_r($function);

			echo ' (' . $function['accepted_args'] . ') <br>';
		}
	}

	echo '</pre>';
}