Best collection of code for your 'functions.php' file [closed]

Question

As with many others who are now viewing this post, I have been reading various blogs, forums, and discussion groups to learn and improve my WordPress skills. Over the past 12 months I have been on a mission to substitute my use of plugins by adding code to my functions.php file instead.

While I completely agree that plugins are very useful in many situations, my experience proved that in 90% of usage cases although a plugin might exist, actually utilizing it could create unnecessary complications and compatibility issues. Additionally in a great deal of cases such plugins added menus and other admin elements which I don't want or need.

More often than not I have found that by analyzing the code of plugins I was able to strip out the piece of code I wanted and hard code it into my functions.php. This provided me with the exact functionality I needed without having to include unnecessary elements.

So, the purpose of this post is my attempt to engage you, the reader/admin/developer, to share with me and other here any code bits which you find useful and have added to your theme's function.php file to extend or enhance WordPress without utilizing a plugin.

When you submit a response here please kindly give each code bit a title, let us know if with what version of WordPress you know its compatible with, include whatever description you feel best describes its function and (if applicable) include a link to the original plugin or source where you found the information.

I am looking forward to all your responses and will of course continually add my own new finds whenever I find them.

_{Please vote on the question and any answers you find useful by clicking on the up arrow on the left hand side of the question or answer.}

Answer 1

Displaying information for logged in users

if ( is_user_logged_in() ) {

}

is not working in functions.php file. You can use this code:

if ( !function_exists('is_user_logged_in') ) :

 function is_user_logged_in() {
$user = wp_get_current_user();

if ( $user->id == 0 ){
// This section if user is not logged in
} else {
// This section if user is logged in
}
}
endif;

Answer 2

Automatically adding header images from directory location

Within the default them which comes with wordpress you will notice an additional theme menu which gets activated that lets you select a header image to be utilized. Within the default theme code these images are hardcoded into the functions.php file. The code below allows wordpress to automatically pick up new images based upon a specific header image directly you can create on your server (or within your themes folder).

It will automatically include any .jpg or .jpeg files. Every image must have a associating thumbnail file but this can just be a copy of the original with a different name with a file name that has to end in "-thumbnail". The associating name is used as the description in the headers appearance settings and underscores are automatically replaced with spaces. (e.g. My_Header_Image_A.jpg, My_Header_Image_A=thumbnail.jpg will have a description automatically presented a “My Header Image A”)

if ($handle = opendir( TEMPLATEPATH . '/images/headers/') ) {
    $headers = array();
    while (false !== ($file = readdir($handle))) {
        $pos = strrpos( $file, '.' );
        if( $pos !== false && $pos > 0 ) {
            $file_name = substr( $file, 0, $pos );
            if( strpos( $file_name, "-thumbnail" ) === false ) {
                $file_ext = substr( $file, $pos+1 );
                $file_ext_low = strtolower( $file_ext );
                if( $file_ext_low == "jpg" || $file_ext_low == "jpeg" ) {
                    $headers[$file_name] = array (
                    'url' => '%s/images/headers/' . $file,
                    'thumbnail_url' => '%s/images/headers/' . $file_name ."-thumbnail." . $file_ext,
                    'description' => __( str_replace( "_", " ", $file_name ), 'twentyten' )
                    );
                }
            }
        }
    }
closedir($handle);
register_default_headers( $headers );
}

Answer 3

Custom Logos for Login page and Admin

/*-----------------------------------------------------------------------------------*/
/*  Custom logos
/*-----------------------------------------------------------------------------------*/
function custom_admin_logo() {
    echo '
        <style type="text/css">
            #header-logo { background-image: url('.get_bloginfo('template_directory').'/path/to/images/admin-logo.png) !important; }
        </style>
    ';
}
add_action('admin_head', 'custom_admin_logo');

function custom_login_logo() {
    echo '<style type="text/css">
        h1 a { background-image:url('.get_bloginfo('template_directory').'/path/to/images/login-logo.png) !important; }
    </style>';
}

add_action('login_head', 'custom_login_logo');

Answer 4

Remove Admin (User #1) from User list

function your_pre_user_query($user_search) {
  $user = wp_get_current_user();
  if ($user->ID!=1) {
    global $wpdb;
    $user_search->query_where = str_replace('WHERE 1=1',
      "WHERE 1=1 AND {$wpdb->users}.ID<>1",$user_search->query_where);
  }
}
add_action('pre_user_query','your_pre_user_query');

Answer 5

Get Attributes of Given Thumbnail

Use this function with the loop to determine width, height and URL of a thumbnailed image. Very handy for assigning a thumbnailed image as a background element via inline CSS.

/**
* GET THUMBNAIL ATTRIBUTES
*
* Fetches width, heigth and URI of a thumbnail.
*
* @author Philip Downer <[email protected]>
* @license http://opensource.org/licenses/gpl-license.php GNU Public License
* @version v1.0
*
* @param string $return Accepts 'path', 'width', or 'height'.
* @param string $size The thumbnail size corresponding to {@link add_image_size() WP core function}.
* @return mixed Returns the requested info, or if no 'Featured Image' assigned, returns 'false'.
*/
function get_thumb_attr($return,$size='thumbnail') {
    global $post;

    if (has_post_thumbnail($post->ID)) {
      $thumb = wp_get_attachment_image_src(get_post_thumbnail_id(), 'intro');
      if ( $return == 'path' ) { return $thumb[0]; }
      if ( $return == 'width' ) { return $thumb[1]; }
      if ( $return == 'height' ) { return $thumb[2]; }
    } else {
        return false;
    }
}//end function

Answer 6

Output the contents of a widget outside the context of a sidebar using it's ID. The wrapping before/after HTML is not included. You need to know the specific ID of the widget you're angling for (ie 'text-5').

function widget_contents($id) {
    list($type,$number) = explode('-',$id);
    global $wp_registered_widgets;
    $wp_registered_widgets[$id]['callback'][0]->display_callback(array('widget_id'=>$id),$number);
}

You can peek at the output of wp_get_sidebars_widgets() if you aren't sure of the precise ID you need.

A more complete example lifted from /wp-includes/widgets.php under the dynamic_sidebar() function:

function render_widget($id) {
    global $wp_registered_widgets;
    $params = array_merge(
            array( array('widget_id' => $id, 'widget_name' => $wp_registered_widgets[$id]['name']) ),
            (array) $wp_registered_widgets[$id]['params']
    );
    $classname_ = '';
    foreach ( (array) $wp_registered_widgets[$id]['classname'] as $cn ) {
            if ( is_string($cn) )
                    $classname_ .= '_' . $cn;
            elseif ( is_object($cn) )
                    $classname_ .= '_' . get_class($cn);
    }
    $classname_ = ltrim($classname_, '_');
    $params[0]['before_widget'] = sprintf($params[0]['before_widget'], $id, $classname_);

    if ( is_callable($wp_registered_widgets[$id]['callback']) )
            call_user_func_array($wp_registered_widgets[$id]['callback'], $params);
}

Answer 7

Custom smilies (plugin)

/**
 * Smilies.
 */
function filter_smilies_src($img_src, $img, $siteurl) {
    return plugins_url('', __FILE__) . '/img/smilies/' . $img;
}
add_filter('smilies_src', 'filter_smilies_src', 1, 10);

Custom smilies (theme)

/**
 * Smilies.
 */
function filter_smilies_src($img_src, $img, $siteurl) {
    return get_bloginfo('stylesheet_directory') . '/images/smilies/' . $img;
}
add_filter('smilies_src', 'filter_smilies_src', 1, 10);

Answer 8

Automatically close missing tags from the WYSIWYG editor

Tested on: Wordpress 3.0.1

This code will automatically close any missing tags when using the WYSIWYG editor.

// AUTOMATICALLY CLEAN UP HTML WYSIWYG EDITOR BY CLOSING MISSING TAGS
   function clean_bad_content($bPrint = false) {
 global $post;
 $szPostContent  = $post->post_content;
 $szRemoveFilter = array("~<p[^>]*>\s?</p>~", "~<a[^>]*>\s?</a>~", "~<font[^>]*>~", "~<\/font>~", "~style\=\"[^\"]*\"~", "~<span[^>]*>\s?</span>~");
 $szPostContent  = preg_replace($szRemoveFilter, '', $szPostContent);
 $szPostContent  = apply_filters('the_content', $szPostContent);
 if ($bPrint == false) return $szPostContent; 
 else echo $szPostContent;
   }

Answer 9

Reposition the WYSIWYG Editor through JQUERY

Tested on: Wordpress 3.0.1

This code will allow you to remove specific meta boxes which wordpress adds by default to the POST and PAGES screens.

// REPOSITION WYSIWYG EDITOR THROUGH JQUERY
   add_action('admin_head','admin_head_hook');
   function admin_head_hook() {
 ?><style type="text/css">
  #postdiv.postarea, #postdivrich.postarea { margin:0; }
  #post-status-info { line-height:1.4em; font-size:13px; }
  .custom-wysiwyg-editor-container { margin:2px 6px 6px 6px; }
  #ed_toolbar { display:none; }
  #postdiv #ed_toolbar, #postdivrich #ed_toolbar { display:block; }
 </style><?php
   }

   add_action('admin_footer','admin_footer_hook');
   function admin_footer_hook() {
 ?><script type="text/javascript">
  jQuery('#postdiv, #postdivrich').prependTo('.custom-wysiwyg-editor-container');
 </script><?php
   }

Answer 10

Remove role="search" attributes for get_search_form()

function remove_role_search($role)
{
    $result = array();
    preg_match_all('|role="[^"]*"|U', $role, $result);
    foreach ($result[0] as $role_tag) {
        $role = str_replace($role_tag, '', $role);
    }
    return $role;
}
add_filter('get_search_form', 'remove_role_search');

Answer 11

Add a Login Link to wp_nav_menu

//ADD LOGIN LINK TO MENU
add_filter('wp_nav_menu_items', 'add_login_logout_link', 10, 2);

function add_login_logout_link($items, $args) { 

        $loginoutlink = wp_loginout('index.php', false); 

        $items .= '<li>'. $loginoutlink .'</li>'; 

    return $items; 
}

Answer 12

Changing "Posts" menu name in admin to whatever you wish (e.g. "Articles")

// hook the translation filters
add_filter('gettext','change_post_to_article');
add_filter('ngettext','change_post_to_article');

function change_post_to_article( $translated ) {
$translated = str_ireplace('Post','Article',$translated );// ireplace is PHP5 only
return $translated;
}

Credits to smashingmagazine.com

Answer 13

Remove Links Menu Item

Many of my WordPress installs don't require that users have access to the 'Links' menu item. This function removes it from view.

add_action( 'admin_menu', 'custom_admin_menu' );
function custom_admin_menu() 
{
    global $menu;
    // var_dump($menu); // use this to identify the key for the menu item you want to remove
    unset( $menu[15] ); //key 15 is links
    if ( !current_user_can('manage_options') ) { unset( $menu[75] ); } //key 75 is tools ... but only for non super admins
}

Answer 14

Disable Upgrade Now Message for Non-Administrators

I'm actually a big fan of NOT using this code. Instead, I prefer to allow customers to update their own WordPress installs. This helps keep the site up-to-date and forces me to write better code.

if ( !current_user_can( 'manage_options' ) ) {
  add_action( 'init', create_function( '$a', "remove_action( 'init', 'wp_version_check' );" ), 2 );
  add_filter( 'pre_option_update_core', create_function( '$a', "return null;" ) );
}

Answer 15

Automatically add a hidden custom field and associating value to a post when the post is published

add_action('publish_page', 'add_custom_field_automatically');
add_action('publish_post', 'add_custom_field_automatically');
function add_custom_field_automatically($post_ID) {
global $wpdb;
if(!wp_is_post_revision($post_ID)) {
    add_post_meta($post_ID, 'field-name', 'custom value', true);
}
}

Answer 16

Call bloginfo using shortcode...

function digwp_bloginfo_shortcode($atts) {
    
    extract(shortcode_atts(array(
            'key' => '',
            ), $atts));
    
    return get_bloginfo($key);
}

add_shortcode('bloginfo', 'digwp_bloginfo_shortcode');

Usage:

[bloginfo key='name']

Answer 17

Add custom post types to archives page

function namespace_add_custom_types( $query ) {
if( is_category() || is_tag() && empty( $query->query_vars['suppress_filters'] ) ) {
$query->set( 'post_type', array(
 'post', 'your-custom-post-type-here'
            ));
      return $query;
    }
}
add_filter( 'pre_get_posts', 'namespace_add_custom_types' );

Answer 18

Add a custom class to the next and previous links

add_filter('next_posts_link_attributes', 'posts_link_attributes');
add_filter('previous_posts_link_attributes', 'posts_link_attributes');
function posts_link_attributes(){
    return 'class="styled-button"';
    }