42 Extremely Useful Tricks for the WordPress Functions File

The WordPress functions.php file is like a plugin for your WordPress theme, allowing you to add both simple and complex functionality to your site. Below are 42 extremely useful tricks that you can add to your WordPress functions.php file.

Note: Always backup your website before editing the functions.php file, and consider developing on a staging environment first.

1. Hide Admin Bar for Non-Admins
   php

   if (!current_user_can('manage_options')) {
show_admin_bar(false);
}

2. Remove WordPress Version
   php

   remove_action('wp_head', 'wp_generator');

3. Remove RSS Feed Links
   php

   remove_action('wp_head', 'feed_links', 2);

4. Disable XML-RPC
   php

   add_filter('xmlrpc_enabled', '__return_false');

5. Disable Self Pingbacks
   php

   function disable_self_ping(&$links) {
foreach ($links as $l => $link)
if (0 === strpos($link, get_option('home')))
unset($links[$l]);
}
add_action('pre_ping', 'disable_self_ping');


Performance

6. Limit Revisions
   php

   define('WP_POST_REVISIONS', 5);

7. Remove Query Strings
   php

   function remove_query_strings() {
if (!is_admin()) {
add_filter('script_loader_src', 'remove_query_strings_split', 15);
add_filter('style_loader_src', 'remove_query_strings_split', 15);
}
}
function remove_query_strings_split($src){
$output = preg_split("/(&ver|\?ver)/", $src);
return $output[0];
}
add_action('init', 'remove_query_strings');


Customization

8. Add Custom Logo Support
   php

   function theme_prefix_setup() {
add_theme_support('custom-logo');
}
add_action('after_setup_theme', 'theme_prefix_setup');

9. Custom Excerpt Length
   php

   function custom_excerpt_length($length) {
return 20;
}
add_filter('excerpt_length', 'custom_excerpt_length', 999);

10. Custom Excerpt Suffix
    php

    function custom_excerpt_more($more) {
return '...';
}
add_filter('excerpt_more', 'custom_excerpt_more');

11. Register New Sidebar
    php

    function custom_sidebar() {
register_sidebar(array(
'name' => __('Custom Sidebar'),
'id' => 'custom-sidebar',
));
}
add_action('widgets_init', 'custom_sidebar');

12. Custom Login Logo
    php

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


SEO and Social

13. Add Open Graph Meta
    php

    function insert_open_graph_in_head() {
// Your Open Graph Tags here
}
add_action('wp_head', 'insert_open_graph_in_head', 5);

14. Add Canonical Tags
    php

    function rel_canonical() {
if (!is_singular()) return;
global $wp_the_query;
if ($id = $wp_the_query->get_queried_object_id()) {
$link = get_permalink($id);
echo "\n<link rel='canonical' href='$link' />\n";
}
}
add_action('wp_head', 'rel_canonical');

15. Remove Yoast SEO Comment in Head
    php

    add_filter('wpseo_debug_markers', '__return_false');

16. Add Twitter Cards
    php

    function add_twitter_cards() {
// Your Twitter Card data here
}
add_action('wp_head', 'add_twitter_cards');


Security

17. Disable File Editing from Dashboard
    php

    define('DISALLOW_FILE_EDIT', true);

18. Remove Error Message on Login Page
    php

    function no_wordpress_errors(){
return 'Something is wrong!';
}
add_filter('login_errors', 'no_wordpress_errors');

19. Restrict Access to WP-Admin
    php

    function restrict_admin_access(){
if (!current_user_can('manage_options') && '/wp-admin/admin-ajax.php' != $_SERVER['PHP_SELF']) {
wp_redirect(home_url());
}
}
add_action('admin_init', 'restrict_admin_access', 1);


Advanced Features

20. Add Custom Post Type
    php

    function create_post_type() {
register_post_type('my_custom_post',
array('labels' => array('name' => __('My Custom Post')),
'public' => true,
)
);
}
add_action('init', 'create_post_type');

21. Custom Dashboard Widgets
    php

    function add_custom_dashboard_widgets() {
wp_add_dashboard_widget('custom_help_widget', 'Theme Support', 'custom_dashboard_help');
}
function custom_dashboard_help() {
echo '<p>Welcome to my custom dashboard widget.</p>';
}
add_action('wp_dashboard_setup', 'add_custom_dashboard_widgets');

22. Register Custom Taxonomy
    php

    function create_custom_taxonomy() {
$labels = array(
'name' => _x('Taxonomies', 'taxonomy general name'),
// Other labels here
);
register_taxonomy('taxonomy', array('post'), array(
'label' => __('Custom Taxonomy'),
'labels' => $labels,
// Additional options here
));
}
add_action('init', 'create_custom_taxonomy', 0);


WooCommerce Customization

23. Remove WooCommerce Breadcrumbs
    php

    remove_action('woocommerce_before_main_content', 'woocommerce_breadcrumb', 20, 0);

24. Change Add to Cart Text on WooCommerce Button
    php

    add_filter('woocommerce_product_single_add_to_cart_text', 'woo_custom_cart_button_text');
function woo_custom_cart_button_text() {
return __('My Button Text', 'woocommerce');
}

25. Hide Out of Stock Items
    php

    add_filter('woocommerce_product_query_meta_query', 'hide_out_of_stock_items');
function hide_out_of_stock_items($meta_query){
$meta_query[] = array(
'key' => '_stock_status',
'value' => 'outofstock',
'compare' => '!='
);
return $meta_query;
}


Posts and Pages

26. Change Read More Link
    php

    function modify_read_more_link() {
return '<a class="more-link" href="' . get_permalink() . '">Your Read More Link Text</a>';
}
add_filter('the_content_more_link', 'modify_read_more_link');

27. Add Featured Image Support
    php

    add_theme_support('post-thumbnails');

28. Remove Sticky Post Class
    php

    function remove_sticky_class($classes) {
if(in_array('sticky', $classes)) {
$classes = array_diff($classes, array('sticky'));
$classes[] = 'my-sticky';
}
return $classes;
}
add_filter('post_class','remove_sticky_class');

29. Redirect To Home After Logout
    php

    function logout_redirect_home(){
wp_redirect( home_url() );
exit();
}
add_action('wp_logout','logout_redirect_home');


Miscellaneous

30. Change Admin Footer Text
    php

    function custom_admin_footer_text () {
echo 'Your custom admin footer text';
}
add_filter('admin_footer_text', 'custom_admin_footer_text');

31. Disable WP Emojis
    php

    remove_action('wp_head', 'print_emoji_detection_script', 7);
remove_action('wp_print_styles', 'print_emoji_styles');

32. Enable SVG Uploads
    php

    function enable_svg_upload($mimes) {
$mimes['svg'] = 'image/svg+xml';
return $mimes;
}
add_filter('upload_mimes', 'enable_svg_upload');

33. Disable WordPress Update Notifications for Specific Plugin
    php

    function disable_plugin_updates( $value ) {
if ( isset($value) && is_object($value) && isset($value->response['plugin-folder/plugin-file.php']) ) {
unset($value->response['plugin-folder/plugin-file.php']);
}
return $value;
}
add_filter('site_transient_update_plugins', 'disable_plugin_updates');

34. Customize the Login Page URL
    php

    function custom_loginlogo_url($url) {
return get_bloginfo('url');
}
add_filter('login_headerurl', 'custom_loginlogo_url');

35. Add Categories to Attachments
    php

    function add_categories_to_attachments() {
register_taxonomy_for_object_type( 'category', 'attachment' );
}
add_action( 'init' , 'add_categories_to_attachments' );

36. Add Custom Role
    php

    add_role('custom_role', 'Custom Role', array('read' => true));

37. Automatically Set the Featured Image
    php

    function autoset_featured_image() {
global $post;
if (!has_post_thumbnail($post->ID)) {
$attached_image = get_children("post_parent=$post->ID&post_type=attachment&post_mime_type=image&numberposts=1");
if ($attached_image) {
foreach ($attached_image as $attachment_id => $attachment) {
set_post_thumbnail($post->ID, $attachment_id);
}
}
}
}
add_action('the_post', 'autoset_featured_image');

38. Add Custom Image Sizes
    php

    function my_custom_sizes() {
add_image_size('my-custom-size', 400, 300, true);
}
add_action('after_setup_theme', 'my_custom_sizes');

39. Move jQuery to the Footer
    php

    function move_jquery_to_footer() {
if (!is_admin()) {
wp_deregister_script('jquery');
wp_register_script('jquery', includes_url('/js/jquery/jquery.js'), false, null, true);
wp_enqueue_script('jquery');
}
}
add_action('wp_enqueue_scripts', 'move_jquery_to_footer');

40. Change Howdy Text in Admin Bar
    php

    function replace_howdy($wp_admin_bar) {
$my_account=$wp_admin_bar->get_node('my-account');
$newtitle = str_replace('Howdy,', 'Welcome,', $my_account->title);
$wp_admin_bar->add_node(array(
'id' => 'my-account',
'title' => $newtitle,
));
}
add_filter('admin_bar_menu', 'replace_howdy',25);

41. Remove Unused Dashboard Widgets
    php

    function remove_dashboard_widgets() {
global $wp_meta_boxes;
unset($wp_meta_boxes['dashboard']['normal']['core']['dashboard_incoming_links']);
unset($wp_meta_boxes['dashboard']['normal']['core']['dashboard_plugins']);
}
add_action('wp_dashboard_setup', 'remove_dashboard_widgets' );

42. Change Admin Email Without Confirmation
    php

    add_filter( 'admin_email_check_interval', '__return_false' );

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