Posts Issued in August, 2014

// Register a new shortcode: [book]
add_shortcode( 'book', 'ssd_sc1_book' );
 
// The callback function that will replace [book]
function ssd_sc1_book() {
    return 'http://www.amazon.com/dp/0470560541';
}
 
 
//shortcode with parameters
// Register a new shortcode: [books title="xxx"]
add_shortcode( 'books', 'ssd_sc2_multiple_books' );
 
// The callback function that will replace [books]
function ssd_sc2_multiple_books( $attr ) {
    switch( $attr['title'] ) {
        case 'xkcd':
            $isbn = '0615314465';
            $title = 'XKCD Volume 0';
            break;
 
        default:
        case 'prowp':
            $isbn = '0470560541';
            $title = 'Profesional WordPress';
            break;
    }
 
    return "<a href='http://www.amazon.com/dp/$isbn'>$title</a>";
}
 
/*The anchor text in the Amazon link will now be parameterized. this time with a second parameter $content , which will receive any enclosed text as a string. Replace [amazon isbn=”xxx”]book title[/amazon] */
// Register a new shortcode: [amazon isbn="123"]link title[/amazon]
add_shortcode( 'amazon', 'ssd_sc3_amazon' );
 
// Callback function for the [amazon] shortcode
function ssd_sc3_amazon( $attr, $content ) {
 
    // Get ISBN or set default
    if( isset( $attr['isbn'] ) ) {
        $isbn = preg_replace( '/[^\d]/', '', $attr['isbn'] );
    } else {
        $isbn = '0470560541';
    }
 
    // Sanitize content, or set default
    if( !empty( $content ) ) {
        $content = esc_html( $content );
    } else {
        if( $isbn == '0470560541' ) {
            $content = 'Professional WordPress';
        } else {
            $content = 'this book';
        }
    }
 
    return "<a href='http://www.amazon.com/dp/$isbn'>$content</a>";
}

<?php
/*
Plugin Name: Shortcode Example 4
Plugin URI: http://example.com/
Description: Replace [amazonimg] with images from Amazon
Version: 1.0
*/
 
// Register shortcodes [amazonimage] and [amazonimg]
add_shortcode( 'amazonimage', 'ssd_sc4_amazonimage' );
add_shortcode( 'amazonimg', 'ssd_sc4_amazonimage' );
 
// Callback function for the [amazonimage] shortcode
function ssd_sc4_amazonimage( $attr, $content ) {
 
    // Get ASIN or set default
    $possible = array( 'asin', 'isbn' );
    $asin = ssd_sc4_find( $possible, $attr, '0470560541' );
 
    // Get affiliate ID or set default
    $possible = array( 'aff', 'affiliate' );
    $aff = ssd_sc4_find( $possible, $attr, 'aff_id' );
 
    // Get image size if specified
    $possible = array( 'size', 'image', 'imagesize' );
    $size = ssd_sc4_find( $possible, $attr, '' );
 
    // Get type if specified
    if( isset( $attr['type'] ) ) {
        $type = strtolower( $attr['type'] );
        $type = ( $type == 'cd' or $type == 'disc' ) ? 'cd' : '';
    }
 
    // Now build the Amazon image URL
    $img = 'http://images.amazon.com/images/P/';
    $img .= $asin;
    // Image option: size
    if( $size ) {
        switch( $size ) {
            case 'small':
                $size = '_AA100';
                break;
            default:
            case 'medium':
                $size = '_AA175';
                break;
            case 'big':
            case 'large':
                $size = '_SCLZZZZZZZ';
        }
    }
    // Image option: type
    if( $type == 'cd' ) {
        $type = '_PF';
    }
    // Append options to image URL, if any
    if( $type or $size ) {
        $img .= '.01.'.$type.$size;
    }
    // Finish building the image URL
    $img .= '.jpg';
 
    // Now return the image
    return "<a href='http://www.amazon.com/dp/$asin'><img src='$img' /></a>";
}
 
// Helper function:
// Search $find_keys in array $in_array, return $default if not found
function ssd_sc4_find( $find_keys, $in_array, $default ) {
    foreach( $find_keys as $key ) {
        if( isset( $in_array[$key] ) )
            return $in_array[$key];
    }
    return $default;
}

$shortcode_tags = array (
‘wp_caption’ = > ‘img_caption_shortcode’,
‘caption’ = > ‘img_caption_shortcode’,
‘gallery’ = > ‘gallery_shortcode’,
‘embed’ = > ‘__return_false’,
‘amazonimage’ = > ‘ssd_sc4_amazonimage’,
‘amazonimg’ = > ‘ssd_sc4_amazonimage’,
)

/*
Plugin Name: Shortcode Example 5
Plugin URI: http://example.com/
Description: Recursive [b] and [i] shortcodes
Version: 1.0
*/
 
// add shortcodes [b] and [i]
add_shortcode( 'i', 'ssd_sc5_italic' );
add_shortcode( 'b', 'ssd_sc5_bold' );
 
// callback function: return bold text
function ssd_sc5_bold( $attr, $content ) {
    return "<strong>".do_shortcode( $content )."</strong>";
}
 
// callback function: return italic text
function ssd_sc5_italic( $attr, $content ) {
    return "<em>".do_shortcode( $content )."</em>";
}

<?php
/*
Plugin Name: Shortcode Example 6
Plugin URI: http://example.com/
Description: Enables [url] and [b] shortcodes in comments
Version: 1.0
*/
 
// Hook into 'comment_text' to process comment content
add_filter( 'comment_text', 'ssd_sc6_comments' );
 
// This function processes comment content
function ssd_sc6_comments( $comment ) {
 
    // Save registered shortcodes:
    global $shortcode_tags;
    $original = $shortcode_tags;
 
    // Unregister all shortcodes:
    remove_all_shortcodes();
 
    // Register new shortcodes:
    add_shortcode( 'url', 'ssd_sc6_comments_url' );
    add_shortcode( 'b', 'ssd_sc6_comments_bold' );
    add_shortcode( 'strong', 'ssd_sc6_comments_bold' );
 
    // Strip all HTML tags from comments:
    $comment = wp_strip_all_tags( $comment );
 
    // Process comment content with these shortcodes:
    $comment = do_shortcode( $comment );
 
    // Unregister comment shortcodes, restore normal shortcodes
    $shortcode_tags = $original;
 
    // Return comment:
    return $comment;
}
 
// the [b] or [strong] to <strong> callback
function ssd_sc6_comments_bold( $attr, $text ) {
    return "<strong>".do_shortcode( $text )."</strong>";
}
 
// the [url] to <a> callback
function ssd_sc6_comments_url( $attr, $text ) {
    $text = esc_url( $text );
    return "<a href=\"$text\">$text</a>";
}

<?php
/*
Plugin Name: Shortcode Example 8
Plugin URI: http://example.com/
Description: Various shortcodes: [24hours], [members], [email]
Version: 1.0
*/
 
add_shortcode( '24hours', 'ssd_sc8_24hours' );
 
function ssd_sc8_24hours( $attr, $content ) {
    $now = time();
    $post_time = get_the_date( 'U' );
    if( ( $now - $post_time ) > 86400 ) {
        return 'Offer has expired!';
    } else {
        return $content;
    }
}
 
add_shortcode( 'members', 'ssd_sc8_loggedin' );
 
function ssd_sc8_loggedin( $attr, $content ) {
    if( is_user_logged_in() ) {
        return $content;
    } else {
        return "<p>Members Eyes Only</p>";
    }
}
 
add_shortcode( 'email', 'ssd_sc8_email' );
 
function ssd_sc8_email( $attr, $content ) {
    if( is_email( $content ) ) {
        return sprintf( '<a href="mailto:%s">%s</a>',
            antispambot( $content ),
            antispambot( $content )
        );
    } else {
        return '';
    }
}

//Checking if a Table Already Exists
$tablename = $wpdb- > prefix . “hits”;
if( $wpdb- > get_var(“SHOW TABLES LIKE ‘$tablename’”) != $tablename ) {
// table does not exist!
}

<?php
/*
Plugin Name: User Avatars
Plugin URI: http://example.com
Description: Displays user avatars based on role.
*/
 
function boj_user_avatars( $role = 'subscriber' ) {
 
    /* Get the users based on role. */
    $users = get_users(
        array(
            'role' => $role
        )
    );
 
    /* Check if any users were returned. */
    if ( is_array( $users ) ) {
 
        /* Loop through each user. */
        foreach ( $users as $user ) {
 
            /* Display ther user's avatar. */
            echo get_avatar( $user );
        }
    }
}
 
?>

/* Add a filter to the hook. */
add_filter( 'user_contactmethods', 'ssd_user_contactmethods' );
 
/* Function for adding new contact methods. */
function ssd_user_contactmethods( $user_contactmethods ) {
 
    /* Add the Twitter contact method. */
    $user_contactmethods['twitter'] = 'Twitter Username';
 
    /* Add the phone number contact method. */
    $user_contactmethods['phone'] = 'Phone Number';
 
    /* Return the array with the new values added. */
    return $user_contactmethods;
}

<?php
/*
Plugin Name: User Favorite Post
Plugin URI: http://example.com
Description: Allows users to select their favorite post from the site.
Version: 0.1
 
*/
 
/* Add the post form to the user/profile edit page in the admin. */
add_action( 'show_user_profile', 'ssd_user_favorite_post_form' );
add_action( 'edit_user_profile', 'ssd_user_favorite_post_form' );
 
/* Function for displaying an extra form on the user edit page. */
function ssd_user_favorite_post_form( $user ) {
 
    /* Get the current user's favorite post. */
    $favorite_post = get_user_meta( $user->ID, 'favorite_post', true );
 
    /* Get a list of all the posts. */
    $posts = get_posts( array( 'numberposts' => -1 ) );
    ?>
 
    <h3>Favorites</h3>
 
    <table class="form-table">
 
        <tr>
            <th><label for="favorite_post">Favorite Post</label></th>
 
            <td>
                <select name="favorite_post" id="favorite_post">
                    <option value=""></option>
 
                <?php foreach ( $posts as $post ) { ?>
                    <option value="<?php echo esc_attr( $post->ID ); ?>" 
                    <?php selected( $favorite_post, $post->ID ); ?>>
                        <?php echo esc_html( $post->post_title ); ?>
                    </option>
                <?php } ?>
 
                </select>
                <br />
                <span class="description">Select your favorite post.</span>
            </td>
        </tr>
 
    </table>
<?php }
 
/* Add the update function to the user update hooks. */
add_action( 'personal_options_update', 'ssd_user_favorite_post_update' );
add_action( 'edit_user_profile_update', 'ssd_user_favorite_post_update' );
 
/* Function for updating the user's favorite post. */
function ssd_user_favorite_post_update( $user_id ) {
 
    /* Check if the current user has permission to edit the user. */
    if ( !current_user_can( 'edit_user', $user_id ) )
        return false;
 
    /* Only accept numbers 0-9 since it's a post ID. */
    $favorite_post = preg_replace( "/[^0-9]/", '', $_POST['favorite_post'] );
 
    /* Update the user's favorite post. */
    update_user_meta( $user_id, 'favorite_post', $favorite_post );
}
 
?>

<?php
/*
Plugin Name: Restrict Admin Post Editing
Plugin URI: http://example.com
Description: Only admins can edit posts made by admins.
Version: 0.1
 
*/
 
/* Filter the 'map_meta_cap' hook. */
add_filter( 'map_meta_cap', 'ssd_restrict_admin_post_editing', 10, 4 );
 
/* Function for restricting users from editing admin posts. */
function ssd_restrict_admin_post_editing( $caps, $cap, $user_id, $args ) {
 
    /* If user is trying to edit or delete a post. */
    if ( 'edit_post' == $cap || 'delete_post' == $cap ) {
 
        /* Get the post object. */
        $post = get_post( $args[0] );
 
        /* If an admin is the post author. */
        if ( author_can( $post, 'delete_users' ) ) {
 
            /* Add a capability that only admins might have to the caps array. */
            $caps[] = 'delete_users';
        }
    }
 
    /* Return the array of capabilities. */
    return $caps;
}
 
?>

<?php
/*
Plugin Name: Private Content
Plugin URI: http://example.com
Description: Shortcode for hiding private content.
Version: 0.1
 
*/
 
/* Register shortcodes in 'init'. */
add_action( 'init', 'ssd_private_content_register_shortcodes' );
 
/* Function for registering the shortcode. */
function ssd_private_content_register_shortcodes() {
 
    /* Adds the [ssd-private] shortcode. */
    add_shortcode( 'ssd-private', 'ssd_private_content_shortcode' );
}
 
/* Function for handling shortcode output. */
function ssd_private_content_shortcode( $attr, $content = null ) {
 
    /* If there is no content, return. */
    if ( is_null( $content ) )
        return $content;
 
    /* Check if the current user has the 'read_private_content' capability. */
    if ( current_user_can( 'read_private_content' ) ) {
 
        /* Return the private content. */
        return $content;
    }
 
    /* If the user doesn't have the 'read_private_content' capability. */
    else {
 
        /* Return an alternate message. */
        return '<p>You do not have permission to read this content.</p>';
    }
 
    /* Return an empty string as a fallback. */
    return '';
}
 
?>

<?php
/*
Plugin Name: Forum Roles
Plugin URI: http://example.com
Description: Creates custom roles and capabilities for a fictional forum plugin.
Version: 0.1
 
*/
 
/* Custom forum roles and capabilities class. */
class ssd_Forum_Roles {
 
    /* PHP4 Constructor method. */
    function ssd_Forum_Roles() {
 
        /* Register plugin activation hook. */
        register_activation_hook( __FILE__, array( &$this, 'activation' ) );
 
        /* Register plugin deactivation hook. */
        register_deactivation_hook( __FILE__, array( &$this, 'deactivation' ) );
    }
 
    /* Plugin activation method. */
    function activation() {
 
        /* Get the default administrator role. */
        $role =& get_role( 'administrator' );
 
        /* Add forum capabilities to the administrator role. */
        if ( !empty( $role ) ) {
            $role->add_cap( 'publish_forum_topics' );
            $role->add_cap( 'edit_others_forum_topics' );
            $role->add_cap( 'delete_forum_topics' );
            $role->add_cap( 'read_forum_topics' );
        }
 
        /* Create the forum administrator role. */
        add_role(
            'forum_administrator',
            'Forum Administrator',
            array(
                'publish_forum_topics',
                'edit_others_forum_topics',
                'delete_forum_topics',
                'read_forum_topics'
            )
        );
 
        /* Create the forum moderator role. */
        add_role(
            'forum_moderator',
            'Forum Moderator',
            array(
                'publish_forum_topics',
                'edit_others_forum_topics',
                'read_forum_topics'
            )
        );
 
        /* Create the forum member role. */
        add_role(
            'forum_member',
            'Forum Member',
            array(
                'publish_forum_topics',
                'read_forum_topics'
            )
        );
 
        /* Create the forum suspended role. */
        add_role(
            'forum_suspended',
            'Forum Suspended',
            array( 'read_forum_topics' )
        );
    }
 
    /* Plugin deactivation method. */
    function deactivation() {
 
        /* Get the default administrator role. */
        $role =& get_role( 'administrator' );
 
        /* Remove forum capabilities to the administrator role. */
        if ( !empty( $role ) ) {
            $role->remove_cap( 'publish_forum_topics' );
            $role->remove_cap( 'edit_others_forum_topics' );
            $role->remove_cap( 'delete_forum_topics' );
            $role->remove_cap( 'read_forum_topics' );
        }
 
        /* Set up an array of roles to delete. */
        $roles_to_delete = array(
            'forum_administrator',
            'forum_moderator',
            'forum_member',
            'forum_suspended'
        );
 
        /* Loop through each role, deleting the role if necessary. */
        foreach ( $roles_to_delete as $role ) {
 
            /* Get the users of the role. */
            $users = get_users( array( 'role' => $role ) );
 
            /* Check if there are no users for the role. */
            if ( count( $users ) <= 0 ) {
 
                /* Remove the role from the site. */
                remove_role( $role );
            }
        }
    }
}
 
$forum_roles = new ssd_Forum_Roles();
 
?>

<?php
/*
Plugin Name: Settings API example
Plugin URI: http://example.com/
Description: A complete and practical example of use of the Settings API. This plugin creates a new plugin administration page.
*/
 
// Add a menu for our option page
add_action('admin_menu', 'ssd_myplugin_add_page');
function ssd_myplugin_add_page() {
    add_options_page( 'My Plugin', 'My Plugin', 'manage_options', 'ssd_myplugin', 'ssd_myplugin_option_page' );
}
 
// Draw the option page
function ssd_myplugin_option_page() {
    ?>
    <div class="wrap">
        <?php screen_icon(); ?>
        <h2>My plugin</h2>
        <form action="options.php" method="post">
            <?php settings_fields('ssd_myplugin_options'); ?>
            <?php do_settings_sections('ssd_myplugin'); ?>
            <input name="Submit" type="submit" value="Save Changes" />
        </form>
    </div>
    <?php
}
 
// Register and define the settings
add_action('admin_init', 'ssd_myplugin_admin_init');
function ssd_myplugin_admin_init(){
    register_setting(
        'ssd_myplugin_options',
        'ssd_myplugin_options',
        'ssd_myplugin_validate_options'
    );
    add_settings_section(
        'ssd_myplugin_main',
        'My Plugin Settings',
        'ssd_myplugin_section_text',
        'ssd_myplugin'
    );
    add_settings_field(
        'ssd_myplugin_text_string',
        'Enter text here',
        'ssd_myplugin_setting_input',
        'ssd_myplugin',
        'ssd_myplugin_main'
    );
}
 
// Draw the section header
function ssd_myplugin_section_text() {
    echo '<p>Enter your settings here.</p>';
}
 
// Display and fill the form field
function ssd_myplugin_setting_input() {
    // get option 'text_string' value from the database
    $options = get_option( 'ssd_myplugin_options' );
    $text_string = $options['text_string'];
    // echo the field
    echo "<input id='text_string' name='ssd_myplugin_options[text_string]' type='text' value='$text_string' />";
}
 
// Validate user input (we want text only)
function ssd_myplugin_validate_options( $input ) {
    $valid['text_string'] = preg_replace( '/[^a-zA-Z]/', '', $input['text_string'] );
 
    if( $valid['text_string'] != $input['text_string'] ) {
        add_settings_error(
            'ssd_myplugin_text_string',
            'ssd_myplugin_texterror',
            'Incorrect value entered!',
            'error'
        );        
    }
 
    return $valid;
}

<?php
/*
Plugin Name: Settings API example 2
Plugin URI: http://example.com/
Description: A complete and practical example of use of the Settings API. This one adds a field to the Privacy Settings page
*/
 
// Register and define the settings
add_action('admin_init', 'ssd_myplugin_admin_init');
function ssd_myplugin_admin_init(){
    register_setting(
        'privacy', 
        'ssd_myplugin_options',
        'ssd_myplugin_validate_options' 
    );
 
    add_settings_field(
        'ssd_myplugin_text_string',
        'Enter text here',
        'ssd_myplugin_setting_input',
        'privacy',
        'default'
    );
 
}
 
// Display and fill the form field
function ssd_myplugin_setting_input() {
    // get option 'text_string' value from the database
    $options = get_option( 'ssd_myplugin_options' );
    $text_string = $options['text_string'];
    // echo the field
    echo "<input id='text_string' name='ssd_myplugin_options[text_string]' type='text' value='$text_string' />";
}
 
// Validate user input (we want text only)
function ssd_myplugin_validate_options( $input ) {
    $valid['text_string'] = preg_replace( '/[^a-zA-Z]/', '', $input['text_string'] );
 
    if( $valid['text_string'] != $input['text_string'] ) {
        add_settings_error(
            'ssd_myplugin_text_string',
            'ssd_myplugin_texterror',
            'Incorrect value entered!',
            'error'
        );        
    }
 
    return $valid;
}

<?php
/*
Plugin Name: Transients API example
Plugin URI: http://example.com/
Description: Sample plugin to illustrate how the Transients API works.
*/
 
// Fictional function that fetchs from an online radio a song title currently on air
function ssd_myplugin_fetch_song_title_from_radio() {
    /*
    Here you would find code fetching data from a remote web site.
    See Chapter 10 to learn how to do this.
 
    In this example we will just return a random song title from a few fictional ones
    */
 
    $titles = array(
        'I Heart WordPress - by  Hackers',
        'Highway to Heaven - by AB/CD',
        'WorpDress Roks - by Miss Spellings',
        'Careful With That Hack, Eugene - by Fink Ployd'
    );
 
    // Get a random song title and return it
    $random = $titles[ mt_rand(0, count($titles) - 1) ];
    return $random;
}
 
// Get song title from database and return it
function ssd_myplugin_get_song_title() {
 
    // Get transient value
    $title = get_transient( 'ssd_myplugin_song' );
 
    // If the transient does not exists or has expired, refresh it
    if( false === $title ) {
        $title = ssd_myplugin_fetch_song_title_from_radio();
        set_transient( 'ssd_myplugin_song', $title, 180 );
    }
 
    return $title;
}

<?php
/*
Plugin Name: Per User Setting example
Plugin URI: http://example.com/
Description: Add a user option in Profile to allow choosing either English or Spanish in the admin area
 
*/
 
// Return user's locale
function ssd_adminlang_set_user_locale() {
    $user = wp_get_current_user();
    $userid = $user->ID;
    $locale = get_user_meta( $userid, 'ssd_adminlang_lang', true );
    return $locale;
}
// Trigger this function every time WP checks the locale value
add_filter( 'locale', 'ssd_adminlang_set_user_locale' );
 
// Add and fill an extra input field to user's profile
function ssd_adminlang_display_field( $user ) {
 
    $userid = $user->ID;
    $lang = get_user_meta( $userid, 'ssd_adminlang_lang', true );
 
    ?>
    <tr>
        <th scope="row">Language</th>
        <td>
            <select name="ssd_adminlang_lang">
                <option value="" <?php selected( '', $lang); ?>>English</option>
                <option value="es_ES" <?php selected( 'es_ES', $lang); ?>>Espa&ntilde;ol</option>
            </select>
        </td>
    </tr>
    <?php
}
add_action( 'personal_options', 'ssd_adminlang_display_field' );
 
// Monitor form submits and update user's setting if applicable
function ssd_adminlang_update_field( $userid ) {
    if( isset( $_POST['ssd_adminlang_lang'] ) ) {
        $lang = $_POST['ssd_adminlang_lang'] == 'es_ES' ? 'es_ES' : '';
        update_user_meta( $userid, 'ssd_adminlang_lang', $lang );
    }
}
add_action( 'personal_options_update', 'ssd_adminlang_update_field' );

<?php
/*
Plugin Name: Simple Debug
Plugin URI: http://example.com/
Description: Append ?debug=1 to any URL to display debug information if you are an admin
*/
 
add_action( 'init', 'ssd_debug_check' );
 
function ssd_debug_check() {
    if( isset( $_GET['debug'] ) && current_user_can( 'manage_options' ) ) {
        if( !defined( 'SAVEQUERIES' ) )
            define( 'SAVEQUERIES', true );
        add_action( 'wp_footer', 'ssd_debug_output' );
    }
}
 
// Print debug information
function ssd_debug_output() {
    global $wpdb;
    echo "<pre>";
    print_r($wpdb->queries);
    echo "</pre>";
}

<?php
/*
Plugin Name: Unused Tags
Plugin URI: http://example.com/
Description: Find unused tags and rename or delete them
*/
 
// Add an entry for our option page to the Posts menu
add_action('admin_menu', 'ssd_utags_add_page');
function ssd_utags_add_page() {
    add_posts_page( 'Unused Tags', 'Unused Tags', 'manage_options',
        'ssd_utags', 'ssd_utags_option_page' );
}
 
// Catch any action parameter in query string
add_action( 'admin_init', 'ssd_utags_do_action' );
 
// Proceed to requested ssd_action if applicable
function ssd_utags_do_action() {
    if( !isset( $_REQUEST['ssd_action'] ) )
        return;
 
    if( !current_user_can( 'manage_options' ) )
        wp_die( 'Insufficient privileges!' );
 
    $id     = $_REQUEST['id'];
    $action = $_REQUEST['ssd_action'];
 
    if( $action == 'done' ) {
        add_action( 'admin_notices', 'ssd_utags_message' );
        return;
    }
 
    check_admin_referer( 'ssd_utags-'.$action.'_tag'.$id );
 
    switch( $action ) {
        case 'rename':
            $newtag = array( 'name' => $_POST['name'], 'slug' => $_POST['name'] );
            wp_update_term( $id, 'post_tag', $newtag );
            break;
        case 'delete':
            wp_delete_term( $id, 'post_tag' );
            break;
    }
 
    wp_redirect( add_query_arg( array( 'ssd_action' => 'done' ) ) );
 
}
 
// Admin notice
function ssd_utags_message() {
    echo "<div class='updated'><p>Action completed</p></div>";
}
 
// Draw the tag management page
function ssd_utags_option_page() {
    ?>
    <div class="wrap">
        <?php screen_icon(); ?>
        <h2>Unused Tags</h2>
 
        <?php
 
        if( $tags = ssd_utags_find_orphans() ):
 
        echo '<p>You currently have '.count( $tags ). ' unused tags:</p>';
        echo '<ol>';
 
        foreach( $tags as $tag ) {
            $id   = $tag->term_id;
            $name = esc_attr( $tag->name );
 
            $delete_url= add_query_arg( array('ssd_action'=>'delete','id'=>$id) );
            $nonced_url= wp_nonce_url( $delete_url, 'ssd_utags-delete_tag'.$id );
            ?>
            <li>
            <form action="" method="post">
            <?php wp_nonce_field( 'ssd_utags-rename_tag'.$id ); ?>
            <input type="hidden" name="ssd_action" value="rename" />
            <input type="hidden" name="id" value="<?php echo $id; ?>" />
            <input type="text" name="name" value="<?php echo $name; ?>" />
            <input type="submit" value="Rename" /> or
            <a href="<?php echo $nonced_url; ?>">delete</a> this tag
            </form>
            </li>
 
        <?php }
 
        else: ?>
        <p>You have no unused tags.</p>
 
        <?php endif; ?>
 
        </ol>
    </div>
    <?php
}
 
// Find unused tags, return them in an array
function ssd_utags_find_orphans() {
    global $wpdb;
 
    $sql = "SELECT terms.term_id, terms.name FROM {$wpdb->terms} terms
            INNER JOIN {$wpdb->term_taxonomy} taxo
            ON terms.term_id=taxo.term_id
            WHERE taxo.taxonomy = 'post_tag'
            AND taxo.count=0";
 
    return $wpdb->get_results( $sql );
}

function ssd_validate_date( $date ) {
    // first test: pattern matching
    if( !preg_match( '!\d{2}/\d{2}/\d{4}!', $date ) )
        return 'wrong pattern';
 
    // second test: is date valid?
    $timestamp = strtotime( $date );
    if( !$ t i m e s t a m p )
        return 'date invalid';
 
    // third test: is the date from the past?
    if( $timestamp <= time() )
        return 'past date';
 
    // So far, so good
    return true;
}
 
// Test it:
 
var_dump( ssd_validate_date( '12/12/99' ) );
// string(12) "wrong pattern"
 
var_dump( ssd_validate_date( '35/30/1980' ) );
// string(12) "date invalid"
 
var_dump( ssd_validate_date( '03/30/1980' ) );
// string(9) "past date"
 
var_dump( ssd_validate_date( '03/30/2020' ) );
// bool(true)

$values = array(
‘column1’ = > ‘some string’,
‘column2’ = > 43
);
$where = array(
‘ID’ = > 1
);
$formats_values = array( ‘%s’, ‘%d’ );
$formats_where = array( ‘%d’ );
$wpdb- > update( $wpdb- > custom, $values, $where, $formats_values, $formats_where );
 
$values = array(
‘column1’ = > ‘new string’,
‘column2’ = > 44
);
$formats_values = array( ‘%s’, ‘%d’ );
$wpdb- > insert( $wpdb- > custom, $values, $formats_values );
 
$sql = “SELECT COUNT(ID) FROM {$wpdb- > posts}
WHERE post_status = ‘publish’ AND post_type = ‘post’”;
$num_of_posts = $wpdb- > get_var( $sql );
 
$sql = “SELECT `user_email`, `user_url`
FROM $wpdb- > users
WHERE user_login = ‘admin’”;
$object = $wpdb- > get_row( $sql, OBJECT );
$array_a = $wpdb- > get_row( $sql, ARRAY_A );
 
$sql = “SELECT `user_email` FROM $wpdb- > users”;
$emails = $wpdb- > get_col( $sql );
 
$sql = “SELECT YEAR(post_date) AS `year`, count(ID) as posts
FROM $wpdb- > posts
WHERE post_type = ‘post’ AND post_status = ‘publish’
GROUP BY YEAR(post_date)
ORDER BY post_date DESC”;
$results = $wpdb- > get_results( $sql, ARRAY_A );
 
$sql = “SELECT YEAR(post_date) AS `year`, count(ID) as posts
FROM $wpdb- > posts
WHERE post_type = ‘post’ AND post_status = ‘publish’
GROUP BY YEAR(post_date)
ORDER BY post_date DESC”;
$results = $wpdb- > get_results( $sql, ARRAY_A );
foreach( $results as $sum ) {
$year = $sum[‘year’];
$count = $sum[‘posts’];
echo “ < p > Posts published in $year: $count < /p > ”;
}
 
$sql = “DELETE from wp_comments
WHERE comment_author_url
LIKE ‘%evil.example.com%’”;
$deleted = $wpdb- > query( $sql );
 
$sql = “UPDATE $wpdb- > posts
SET comment_status = ‘closed’
WHERE post_date < DATE_SUB( NOW(), INTERVAL 90 DAY )
AND post_status = ‘publish’”;
$wpdb- > query( $sql );

<?php
/**
 * Plugin Name: ssd Alert Box
 * Plugin URI: http://example.com
 * Description: A plugin example that places two input buttons in the blog footer that when clicked display an alert box.
 * Version: 0.1
 */
 
/* Add the translation function after the plugins loaded hook. */
add_action( 'plugins_loaded', 'ssd_alert_box_load_translation' );
 
/**
 * Loads a translation file if the paged being viewed isn't in the admin.
 *
 * @since 0.1
 */
function ssd_alert_box_load_translation() {
 
    /* If we're not in the admin, load any translation of our plugin. */
    if ( !is_admin() )
        load_plugin_textdomain( 'ssd-alert-box', false, 'ssd-alert-box/languages' );
}
 
/* Add our script function to the print scripts action. */
add_action( 'wp_print_scripts', 'ssd_alert_box_load_script' );
 
/**
 * Loads the alert box script and localizes text strings that need translation.
 *
 * @since 0.1
 */
function ssd_alert_box_load_script() {
 
    /* If we're in the WordPress admin, don't go any farther. */
    if ( is_admin() )
        return;
 
    /* Get script path and file name. */
    $script = trailingslashit( plugins_url( 'ssd-alert-box' ) ) . 'ssd-alert-box-script.js';
 
    /* Enqueue our script for use. */
    wp_enqueue_script( 'ssd-alert-box', $script, false, 0.1 );
 
    /* Localize text strings used in the JavaScript file. */
    wp_localize_script( 'ssd-alert-box', 'ssd_alert_box_L10n', array(
        'ssd_box_1' => __( 'Alert boxes are annoying!', 'ssd-alert-box' ),
        'ssd_box_2' => __( 'They are really annoying!', 'ssd-alert-box' ),
    ) );
}
 
/* Add our alert box buttons to the site footer. */
add_action( 'wp_footer', 'ssd_alert_box_display_buttons' );
 
/**
 * Displays two input buttons with a paragraph.  Each button has an onClick() event that loads
 * a JavaScript alert box.
 *
 * @since 0.1
 */
function ssd_alert_box_display_buttons() {
 
    /* Get the HTML for the first input button. */
    $ssd_alert_box_buttons = '<input type="button" onclick="ssd_show_alert_box_1()" value="' . esc_attr__( 'Press me!', 'ssd-alert-box' ) . '" />';
 
    /* Get the HTML for the second input button. */
    $ssd_alert_box_buttons .= '<input type="button" onclick="ssd_show_alert_box_2()" value="' . esc_attr__( 'Now press me!', 'ssd-alert-box' ) . '" />';
 
    /* Wrap the buttons in a paragraph tag. */
    echo '<p>' . $ssd_alert_box_buttons . '</p>';
}
 
?>
 
//Code snippet ssd - alert - box - script.js
/**
 * Displays an alert box with our first translated message when called.
 */
function ssd_show_alert_box_1() {
    alert( ssd_alert_box_L10n.ssd_box_1 );
}
 
/**
 * Displays an alert box with our second translated message when called.
 */
function ssd_show_alert_box_2() {
    alert( ssd_alert_box_L10n.ssd_box_2 );
}

//lang/ssd-alert-box.pot
msgid ""
msgstr ""
"Project-Id-Version: Tricks localizing\n"
"Report-Msgid-Bugs-To: \n"
"POT-Creation-Date: 2013-06-28 23:34-0600\n"
"PO-Revision-Date: 2013-06-28 23:35-0600\n"
"Last-Translator: Serhii <>\n"
"Language-Team: Serhii\n"
"MIME-Version: 1.0\n"
"Content-Type: text/plain; charset=UTF-8\n"
"Content-Transfer-Encoding: 8bit\n"
"X-Poedit-KeywordsList: _e;__;esc_attr_e;esc_attr__;esc_html_e;esc_html__;_x;_ex;esc_attr_x;esc_html_x;_n;_nx;_n_noop;_nx_noop\n"
"X-Poedit-Basepath: ../\n"
"X-Poedit-SearchPath-0: .\n"
 
#: tom-alert-box.php:48
msgid "Alert boxes are annoying!"
msgstr ""
 
#: tom-alert-box.php:49
msgid "They are really annoying!"
msgstr ""
 
#: tom-alert-box.php:65
msgid "Press me!"
msgstr ""
 
#: tom-alert-box.php:68
msgid "Now press me!"
msgstr ""

//Creating a Top - Level Menu
add_menu_page( page_title, menu_title, capability, menu_slug, function, icon_url, position );
 
/*
Plugin Name: WordPress Menu Examples Plugin
Plugin URI: http://example.com/wordpress-plugins/my-plugin
Description: A plugin to create menus and submenus in WordPress
Version: 1.0
License: GPLv2
*/
 
add_action( 'admin_menu', 'ssd_menuexample_create_menu' );
 
function ssd_menuexample_create_menu() {
 
    //create custom top-level menu
    add_menu_page( 'My Plugin Settings Page', 'Menu Example Settings', 'manage_options', __FILE__, 'ssd_menuexample_settings_page', plugins_url( '/images/wp-icon.png', __FILE__ ) );
 
    //create submenu items
    add_submenu_page( __FILE__, 'About My Plugin', 'About', 'manage_options', __FILE__.'_about', ssd_menuexample_about_page );
    add_submenu_page( __FILE__, 'Help with My Plugin', 'Help', 'manage_options', __FILE__.'_help', ssd_menuexample_help_page );
    add_submenu_page( __FILE__, 'Uinstall My Plugin', 'Uninstall', 'manage_options', __FILE__.'_uninstall', ssd_menuexample_uninstall_page ); 
 
}
 
//Adding a Menu Item to an Existing Menu
add_options_page( page_title, menu_title, capability, menu_slug, function);
add_action( 'admin_menu', 'ssd_menuexample_create_menu' );
 
function ssd_menuexample_create_menu() {
 
    //create a submenu under Settings
    add_options_page( 'My Plugin Settings Page', 'Menu Example Settings', 'manage_options', __FILE__, 'ssd_menuexample_settings_page' );
 
}

< ?php
class My_Widget extends WP_Widget {
function My_Widget() {
// processes the widget
}
function form($instance) {
// displays the widget form in the admin dashboard
}
function update($new_instance, $old_instance) {
// process widget options to save
}
function widget($args, $instance) {
// displays the widget
}
}

//example
// use widgets_init action hook to e xecute custom function
<?php 
/*
Plugin Name: Widget Example Plugin
Plugin URI: http://example.com/wordpress-plugins/my-plugin
Description: A plugin to create widgets in WordPress
Version: 1.0
License: GPLv2
*/
 
// use widgets_init action hook to execute custom function
add_action( 'widgets_init', 'ssd_widgetexample_register_widgets' );
 
 //register our widget
function ssd_widgetexample_register_widgets() {
    register_widget( 'ssd_widgetexample_widget_my_info' );
}
 
//ssd_widget_my_info class
class ssd_widgetexample_widget_my_info extends WP_Widget {
 
    //process the new widget
    function ssd_widgetexample_widget_my_info() {
        $widget_ops = array( 
            'classname' => 'ssd_widgetexample_widget_class', 
            'description' => 'Display a user\'s favorite movie and song.' 
            ); 
        $this->WP_Widget( 'ssd_widgetexample_widget_my_info', 'My Info Widget', $widget_ops );
    }
 
     //build the widget settings form
/*First, you create a $defaults variable to set the default values of each option. In this example, you set only the default title to My Info. Next pull in the instance values; that is, the widget settings that have been saved. If this is a new widget and was just added to a sidebar, there won ’ t be any settings 
saved, so this value will be empty*/
    function form($instance) {
        $defaults = array( 'title' => 'My Info', 'movie' => '', 'song' => '' ); 
        $instance = wp_parse_args( (array) $instance, $defaults );
        $title = $instance['title'];
        $movie = $instance['movie'];
        $song = $instance['song'];
        ?>
            <p>Title: <input class="widefat" name="<?php echo $this->get_field_name( 'title' ); ?>"  type="text" value="<?php echo esc_attr( $title ); ?>" /></p>
            <p>Favorite Movie: <input class="widefat" name="<?php echo $this->get_field_name( 'movie' ); ?>"  type="text" value="<?php echo esc_attr( $movie ); ?>" /></p>
            <p>Favorite Song: <textarea class="widefat" name="<?php echo $this->get_field_name( 'song' ); ?>" / ><?php echo esc_attr( $song ); ?></textarea></p>
        <?php
    }
 
    //save the widget settings
    function update($new_instance, $old_instance) {
        $instance = $old_instance;
        $instance['title'] = strip_tags( $new_instance['title'] );
        $instance['movie'] = strip_tags( $new_instance['movie'] );
        $instance['song'] = strip_tags( $new_instance['song'] );
 
        return $instance;
    }
 
    //display the widget
    function widget($args, $instance) {
        extract($args);
 
        echo $before_widget;
        $title = apply_filters( 'widget_title', $instance['title'] );
        $movie = empty( $instance['movie'] ) ? '&nbsp;' : $instance['movie'];
        $song = empty( $instance['song'] ) ? '&nbsp;' : $instance['song']; 
 
        if ( !empty( $title ) ) { echo $before_title . $title . $after_title; };
        echo '<p>Fav Movie: ' . $movie . '</p>';
        echo '<p>Fav Song: ' . $song . '</p>';
        echo $after_widget;
    }
}
?>

// use widgets_init action hook to execute custom function
add_action( 'widgets_init', 'ssd_awe_register_widgets' );
 
//register our widget
function ssd_awe_register_widgets() {
    register_widget( 'ssd_awe_widget' );
}
 
//ssd_widget_my_info class
class ssd_awe_widget extends WP_Widget {
 
    //process the new widget
    function ssd_awe_widget() {
 
        $widget_ops = array( 
            'classname' => 'ssd_awe_widget_class', 
            'description' => 'Display an RSS feed with options.' 
            ); 
 
        $this->WP_Widget( 'ssd_awe_widget', 'Advanced RSS Widget', $widget_ops );
    }
 
     //build the widget settings form
    function form($instance) {
        $defaults = array( 
            'title' => 'RSS Feed', 
            'rss_feed' => 'http://strangework.com/feed', 
            'rss_items' => '2' 
        ); 
        $instance = wp_parse_args( (array) $instance, $defaults );
        $title = $instance['title'];
        $rss_feed = $instance['rss_feed'];
        $rss_items = $instance['rss_items'];
        $rss_date = $instance['rss_date'];
        $rss_summary = $instance['rss_summary'];
        ?>
            <p>Title: <input class="widefat" name="<?php echo $this->get_field_name( 'title' ); ?>"  type="text" value="<?php echo esc_attr( $title ); ?>" /></p>
            <p>RSS Feed: <input class="widefat" name="<?php echo $this->get_field_name( 'rss_feed' ); ?>"  type="text" value="<?php echo esc_attr( $rss_feed ); ?>" /></p>
            <p>Items to Display:
                <select name="<?php echo $this->get_field_name( 'rss_items' ); ?>">
                    <option value="1" <?php selected( $rss_items, 1 ); ?>>1</option>
                    <option value="2" <?php selected( $rss_items, 2 ); ?>>2</option>
                    <option value="3" <?php selected( $rss_items, 3 ); ?>>3</option>
                    <option value="4" <?php selected( $rss_items, 4 ); ?>>4</option>
                    <option value="5" <?php selected( $rss_items, 5 ); ?>>5</option>
                </select>
            </p>
            <p>Show Date?: <input name="<?php echo $this->get_field_name( 'rss_date' ); ?>"  type="checkbox" <?php checked( $rss_date, 'on' ); ?> /></p>
            <p>Show Summary?: <input name="<?php echo $this->get_field_name( 'rss_summary' ); ?>"  type="checkbox" <?php checked( $rss_summary, 'on' ); ?> /></p>
        <?php
    }
 
    //save the widget settings
    function update($new_instance, $old_instance) {
        $instance = $old_instance;
        $instance['title'] = strip_tags( $new_instance['title'] );
        $instance['rss_feed'] = strip_tags( $new_instance['rss_feed'] );
        $instance['rss_items'] = strip_tags( $new_instance['rss_items'] );
    $instance['rss_date'] = strip_tags( $new_instance['rss_date'] );
    $instance['rss_summary'] = strip_tags( $new_instance['rss_summary'] );
 
        return $instance;
    }
 
    //display the widget
    function widget($args, $instance) {
        extract($args);
 
        echo $before_widget;
 
        //load the widget settings
        $title = apply_filters( 'widget_title', $instance['title'] );
        $rss_feed = empty( $instance['rss_feed'] ) ? '' : $instance['rss_feed'];
        $rss_items = empty( $instance['rss_items'] ) ? 2 : $instance['rss_items'];
        $rss_date = empty( $instance['rss_date'] ) ? 0 : 1; 
        $rss_summary = empty( $instance['rss_summary'] ) ? 0 : 1; 
 
        if ( !empty( $title ) ) { echo $before_title . $title . $after_title; };
 
        if ( $rss_feed ) {
            //display the RSS feed
            wp_widget_rss_output( array(
                'url' => $rss_feed,
                'title' => $title,
                'items' => $rss_items,
                'show_summary' => $rss_summary,
                'show_author' => 0,
                'show_date' => $rss_date
            ) );
        }
 
        echo $after_widget;
    }
}

add_action( 'wp_dashboard_setup', 'ssd_dashboard_example_widgets' );
 
function ssd_dashboard_example_widgets() {
 
    //create a custom dashboard widget
    wp_add_dashboard_widget( 'dashboard_custom_feed', 'My Plugin Information', 'ssd_dashboard_example_display' );
 
}
 
function ssd_dashboard_example_display()
{
    echo '<p>Please contact support@example.com to report bugs.</p>';    
}

<?php 
/*
Plugin Name: RSS Dashboard Widget Example Plugin
Plugin URI: http://example.com/wordpress-plugins/my-plugin
Description: A plugin to create dashboard widgets in WordPress
Version: 1.0
License: GPLv2
*/
 
add_action( 'wp_dashboard_setup', 'ssd_dashboard_example_widgets' );
 
function ssd_dashboard_example_widgets() {
 
    //create a custom dashboard widget
    wp_add_dashboard_widget( 'dashboard_custom_feed', 'My Plugin Information', 'ssd_dashboard_example_display', 'ssd_dashboard_example_setup' );
 
}
 
function ssd_dashboard_example_setup() {
 
    //check if option is set before saving
    if ( isset( $_POST['ssd_rss_feed'] ) ) {
        //retrieve the option value from the form
        $ssd_rss_feed = esc_url_raw( $_POST['ssd_rss_feed'] );
 
        //save the value as an option
        update_option( 'ssd_dashboard_widget_rss', $ssd_rss_feed );
    }
 
     //load the saved feed if it exists
    $ssd_rss_feed = get_option( 'ssd_dashboard_widget_rss ');
 
    ?>
    <label for="feed">
        RSS Feed URL: <input type="text" name="ssd_rss_feed" id="ssd_rss_feed" value="<?php echo esc_url( $ssd_rss_feed ); ?>" size="50" />
    </label>
    <?php
}
 
function ssd_dashboard_example_display()
{
    //load our widget option
    $ssd_option = get_option( 'ssd_dashboard_widget_rss ');
 
    //if option is empty set a default
    $ssd_rss_feed = ( $ssd_option ) ? $ssd_option : 'http://wordpress.org/news/feed/';
 
    //retireve the RSS feed and display it
    echo '<div class="rss-widget">';
 
    wp_widget_rss_output( array(
        'url' => $ssd_rss_feed,
        'title' => 'RSS Feed News',
        'items' => 2,
        'show_summary' => 1,
        'show_author' => 0,
        'show_date' => 1 
    ) );
 
    echo '</div>';    
}
?>

<?php 
/*
Plugin Name: Meta Box Example Plugin
Plugin URI: http://example.com/wordpress-plugins/my-plugin
Description: A plugin to create meta boxes in WordPress
Version: 1.0
License: GPLv2
*/
 
//hook to add a meta box
add_action( 'add_meta_boxes', 'ssd_mbe_create' );
 
function ssd_mbe_create() {
 
    //create a custom meta box
    add_meta_box( 'ssd-meta', 'My Custom Meta Box', 'ssd_mbe_function', 'post', 'normal', 'high' );
 
}
 
function ssd_mbe_function( $post ) {
 
    //retrieve the meta data values if they exist
    $ssd_mbe_name = get_post_meta( $post->ID, '_ssd_mbe_name', true );
    $ssd_mbe_costume = get_post_meta( $post->ID, '_ssd_mbe_costume', true );
 
    echo 'Please fill out the information below';
    ?>
    <p>Name: <input type="text" name="ssd_mbe_name" value="<?php echo esc_attr( $ssd_mbe_name ); ?>" /></p>
    <p>Costume: 
    <select name="ssd_mbe_costume">
        <option value="vampire" <?php selected( $ssd_mbe_costume, 'vampire' ); ?>>Vampire</option>
        <option value="zombie" <?php selected( $ssd_mbe_costume, 'zombie' ); ?>>Zombie</option>
        <option value="smurf" <?php selected( $ssd_mbe_costume, 'smurf' ); ?>>Smurf</option>
    </select>
    </p>
    <?php
}
 
//hook to save the meta box data
add_action( 'save_post', 'ssd_mbe_save_meta' );
 
function ssd_mbe_save_meta( $post_id ) {
 
    //verify the meta data is set
    if ( isset( $_POST['ssd_mbe_name'] ) ) {
 
        //save the meta data
        update_post_meta( $post_id, '_ssd_mbe_name', strip_tags( $_POST['ssd_mbe_name'] ) );
        update_post_meta( $post_id, '_ssd_mbe_costume', strip_tags( $_POST['ssd_mbe_costume'] ) );
 
    }
 
}
?>

< ?php
function ssd_styling_settings() {
? >
< div class=”wrap” >
< h2 > My Plugin < /h2 >
< div id=”message” class=”updated” > Settings saved successfully < /div >
< div id=”message” class=”error” > Error saving settings < /div >
< /div >
< ?php
}
? >

plugin_dir_path( $file );
//$file - (string) (required) — The fi lename of a plugin
 
//determine the local path to your plugin folder
plugin_dir_path( __FILE__ );
 
plugins_url();// Full plugins directory URL
includes_url(); // Full includes directory URL
content_url(); // Full content directory URL (example.com/wp - content )
admin_url(); // Full admin URL
site_url(); // Site URL
home_url(); // Home URL
 
//examples
echo ' < img src=”' .plugins_url( 'images/icon.png' , __FILE__ ). '” > ';

//Plugin Activation Function
register_activation_hook( __FILE__, 'ssd_myplugin_install' );
function ssd_myplugin_install() {
   If ( version_compare( get_bloginfo( 'version' ), '3.1', ' < ' ) ) {
deactivate_plugins( basename( __FILE__ ) ); // Deactivate our plugin
}
 
function ssd_install() {
$ssd_myplugin_options = array(
'view' = > 'grid',
'food' = > 'bacon',
'mode' = > 'zombie'
);
update_option( 'ssd_myplugin_options', $ssd_myplugin_options );
}
}
 
//Plugin Deactivation Function
register_deactivation_hook( __FILE__, 'ssd_myplugin_uninstall' );
function ssd_myplugin_uninstall() {
//do something
}
 
//Uninstall.php - preferred way
// If uninstall not called from WordPress exit
if( !defined( 'WP_UNINSTALL_PLUGIN' ) )
exit ();
// Delete option from options table
delete_option( 'ssd_myplugin_options' );
//remove any additional options and custom tables
 
/*If you delete a plugin in WordPress and
uninstall.php does not exist, WordPress executes the uninstall hook (if it exists).*/
register_activation_hook( __FILE__, 'ssd_myplugin_activate' );
function ssd_myplugin_activate() {
//register the uninstall function
register_uninstall_hook( __FILE__, 'ssd_myplugin_uninstaller' );
}
function ssd_myplugin_uninstaller() {
//delete any options, tables, etc the plugin created
delete_option( 'ssd_myplugin_options' );
}

do_action( $tag, $arg = '' );
do_action('save_post', $post_ID, $post);
//That ' s where plugins come in. You develop custom functions (actions) that perform a specifi c task when the action hook is fi red.
add_action( $tag, $function, $priority, $accepted_args );
add_action( 'wp_footer', 'ssd_example_footer_message', 100 );
function ssd_example_footer_message() {
echo 'This site is built using < a href=”http://wordpress.org”
title=”WordPress publishing platform” > WordPress < /a > .';
}
 
//e xecutes this hook before loading
posts, enabling plugins to change how posts are queried
add_action( 'pre_get_posts', 'ssd_randomly_order_blog_posts' );
function ssd_randomly_order_blog_posts( $query ) {
if ( $query- > is_home & & empty( $query- > query_vars['suppress_filters'] ) )
$query- > set( 'orderby', 'rand' );
}
 
remove_action( $tag, $function_to_remove, $priority, $accepted_args );
remove_all_actions( 'wp_head' );
 
//if a hook has any actions added 
if ( has_action( 'wp_footer' ) )
echo ' < p > An action has been registered for the footer. < /p > ';
else
echo ' < p > An action hasn\'t been registered for the footer. < /p > ';
 
//enables check if an action hook e xecuted
if ( did_action( 'plugins_loaded' ) )
define( 'ssd_MYPLUGIN_READY', true );

/*fi red after most of the WordPress fi les are loaded but before the pluggable functions and WordPress starts e xecuting anything*/
add_action( 'plugins_loaded', 'ssd_footer_message_plugin_setup' );
function ssd_footer_message_plugin_setup() {
/* Add the footer message action. */
add_action( 'wp_footer', 'ssd_example_footer_message', 100 );
}
function ssd_example_footer_message() {
echo 'This site is built using < a href=”http://wordpress.org”
title=”WordPress publishing platform” > WordPress < /a > .';
}
 
/*The init hook is fi red after most of WordPress is set up. Because nearly everything in WordPress is ready at this point, your plugin will probably use this hook for anything it needs to do when all the information from WordPress is available*/
add_action( 'init', 'ssd_add_excerpts_to_pages' );
function ssd_add_excerpts_to_pages() {
add_post_type_support( 'page', array( 'excerpt' ) );
}
 
//The admin_menu hook is called only when an administration page loads
add_action( 'admin_menu', 'ssd_admin_settings_page' );
function ssd_admin_settings_page() {
add_options_page(
'ssd Settings',
'ssd Settings',
'manage_options',
'ssd_admin_settings',
'ssd_admin_settings_page'
);
}
 
/*The template_redirect action hook is important because it ' s the point where WordPress knows which page a user is viewing, but before the theme template is chosen for the
particular page view. It is fi red only on the front end of the site and not in the administration area. This is a good hook to use when you need to load code only for specifi c page views.*/
add_action( 'template_redirect', 'ssd_singular_post_css' );
function ssd_singular_post_css() {
if ( is_singular( 'post' ) ) {
wp_enqueue_style(
'ssd-singular-post',
'ssd-example.css',
false,
0.1,
'screen'
);
}
}
 
/*wp_head - add HTML between the opening < head >and < /head >*/
add_action( 'wp_head', 'ssd_front_page_meta_description' );
function ssd_front_page_meta_description() {
/* Get the site description. */
$description = esc_attr( get_bloginfo( 'description' ) );
/* If a description is set, display the meta element. */
if ( !empty( $description ) )
echo ' < meta name=”description” content=”' . $description . '” / > ';
}

add_filter( $tag, $function, $priority, $accepted_args );
apply_filters( 'wp_title', $title, $sep, $seplocation );
/*wp_title — The name of the hook.
$title — A string and the value that you want to fi lter and return back to WordPress
$sep — A string that tells you what the separator should be between elements in the 
< title > element
$seplocation — The location of the separator.*/
add_filter( 'wp_title', 'ssd_add_site_name_to_title', 10, 2 );
function ssd_add_site_name_to_title( $title, $sep ) {
/* Get the site name. */
$name = get_bloginfo( 'name' );
/* Append the name to the $title variable. */
$title .= $sep . ' ' . $name;
/* Return the title. */
return $title;
}
 
/*
apply_filters_ref_array() function works  same as apply_filters(), butit accepts an array of arguments.
*/
add_filter( 'posts_results', 'ssd_custom_home_page_posts' );
function ssd_custom_home_page_posts( $results ) {
global $wpdb, $wp_query;
/* Check if viewing the home page. */
if ( is_home() ) {
/* Posts per page. */
$per_page = get_option( 'posts_per_page' );
/* Get the current page. */
$paged = get_query_var( 'paged' );
/* Set the $page variable. */
$page = ( ( 0 == $paged || 1 == $paged ) ? 1 : absint( $paged ) );
/* Set the number of posts to offset. */
$offset = ( $page - 1 ) * $per_page . ', ';
/* Set the limit by the $offset and number of posts to show. */
$limits = 'LIMIT '. $offset . $per_page;
/* Get results from the database. */
$results = $wpdb- > get_results( “
S ELECT SQL_CALC_FOUND_ROWS $wpdb- > posts.*
FROM $wpdb- > posts
w h e r e post_type = 'page'
AND post_status = 'publish'
ORDER BY post_title ASC
$limits
“ );
}
return $results;
}
 
remove_filter( $tag, $function_to_remove, $priority, $accepted_args );
remove_all_filters( $tag, $priority );
 
if ( has_filter( 'the_content' ) )
echo 'The content filter hook has at least one filter.';
else
echo 'The content filter hook has no filters.';
 
if ( has_filter( 'the_content', 'wpautop' ) )
echo 'Paragraphs are automatically formatted for the content.';
 
/*current_fi lter is especially useful if you use a single function for multiple hooks but need the function to e xecute differently depending on the hook currently fi ring*/
add_filter( 'the_content', 'ssd_replace_unwanted_words' );
add_filter( 'the_title', 'ssd_replace_unwanted_words' );
function ssd_replace_unwanted_words( $text ) {
/* If the_content is the filter hook, set its unwanted words. */
if ( 'the_content' == current_filter() )
$words = array( 'profanity', 'curse', 'devil' );
/* If the_title is the filter hook, set its unwanted words. */
elseif ( 'the_title' == current_filter() )
$words = array( 'profanity', 'curse' );
/* Replace unwanted words with “Whoops!” */
$text = str_replace( $words, 'Whoops!', $text );
/* Return the formatted text. */
return $text;
}
 
add_filter( 'the_content', 'ssd_add_related_posts_to_content' );
function ssd_add_related_posts_to_content( $content ) {
/* If not viewing a singular post, just return the content. */
if ( !is_singular( 'post' ) )
return $content;
/* Get the categories of current post. */
$terms = get_the_terms( get_the_ID(), 'category' );
/* Loop through the categories and put their IDs in an array. */
$categories = array();
foreach ( $terms as $term )
$categories[] = $term- > term_id;
/* Query posts with the same categories from the database. */
$loop = new WP_Query(
array(
'cat__in' = > $categories,
'posts_per_page' = > 5,
'post__not_in' = > array( get_the_ID() ),
'orderby' = > 'rand'
)
);
/* Check if any related posts exist. */
if ( $loop- > have_posts() ) {
/* Open the unordered list. */
$content .= ' < ul class=”related-posts” > ';
while ( $loop- > have_posts() ) {
$loop- > the_post();
/* Add the post title with a link to the post. */
$content .= the_title(
' < li > < a href=”' . get_permalink() . '” > ',
' < /a > < /li > ',
false
);
}
/* Close the unordered list. */
$content .= ' < /ul > ';
/* Reset the query. */
wp_reset_query();
}
/* Return the content. */
return $content;
}
 
add_filter( 'the_title', 'ssd_strip_tags_from_titles' );
function ssd_strip_tags_from_titles( $title ) {
$title = strip_tags( $title );
return $title;
}
 
add_filter( 'comment_text', 'ssd_add_role_to_comment_text' );
function ssd_add_role_to_comment_text( $text ) {
global $comment;
/* Check if comment was made by a registered user. */
if ( $comment- > user_id > 0 ) {
/* Create new user object. */
$user = new WP_User( $comment- > user_id );
/* If user has a role, add it to the comment text. */
if ( is_array( $user- > roles ) )
$text .= ' < p > User Role: ' . $user- > roles[0] . ' < /p > ';
}
return $text;
}
 
//USING HOOKS FROM WITHIN A CLASS
class ssd_My_Plugin_Loader {
/* Constructor method for the class. */
function ssd_My_Plugin_Loader() {
/* Add the 'singular_check' method to the 'template_redirect' hook. */
add_action( 'template_redirect', array( & $this, 'singular_check' ) );
}
/* Method used as an action. */
function singular_check() {
/* If viewing a singular post, filter the content. */
if ( is_singular() )
add_filter( 'the_content', array( & $this, 'content' ) );
}
/* Method used as a filter. */
function content( $content ) {
/* Get the date the post was last modified. */
$date = get_the_modified_time( get_option( 'date_format' ) );
/* Append the post modified date to the content. */
$content .= ' < p > Post last modified: ' . $date . ' < /p > ';
/* Return the content. */
return $content;
}
}
$ssd_myplugin_loader = new ssd_My_Plugin_Loader();