​The `before_signup_header` action in WordPress allows developers to modify the header section of the Site Sign-up page using PHP code, which can be used for adding custom content or functionality

​The `big_image_size_threshold` WordPress filter adjusts the maximum image size for "BIG images" based on a specified threshold value

​The `bulk_actions-{$this->screen->id}` WordPress PHP filter modifies the items in the bulk actions menu of a specific list table, allowing for customization of the available options

​The `block_editor_preload_paths` filter in WordPress allows developers to modify the array of paths that will be preloaded for the block editor

The 'block_local_requests' filter in WordPress allows developers to restrict access to certain URLs from within the same server. This can be useful for preventing unwanted requests and improving site security.

Learn how to use the WordPress 'check_passwords' PHP action to ensure password security in your website

The 'can_edit_network' PHP filter in WordPress allows site administrators to control user access to network-wide settings and features.

The 'check_admin_referer' PHP action in WordPress is a crucial security measure to prevent unauthorized access.

​The article "Using WordPress `check_ajax_referer` PHP action" explains how to use the `check_ajax_referer` action in WordPress to validate Ajax nonce requests and perform custom actions based on the result