How to use post_class filter in WordPress

post_class filter

Filters the list of CSS class names for the current post.

To use post_class filter, first you have to register it using add_filter. You can write this code into functions.php of your activated theme or in a custom WordPress Plugin.

We at Flipper Code, always prefer to create a custom WordPress Plugin while using hooks so nothing breaks when you update your WordPress Theme in the future.

In the below live example, we have defined a function modify_post_class_defaults which takes 3 parameters and we registered using add_filter. The first parameter post_class is name of the hook, The second parameter modify_post_class_defaults is name of the function which need to be called, third parameter is the priority of calling the hook if same hook is used multiple times and the last parameter is the number of arguments (if any) to be passed in the registered function.

Sometime, you have to remove a registered hook so you can use remove_filter to remove post_class filter.

Parameters

Below are the 3 parameters are required to use this hook.

• $classes : (string[]) An array of post class names.
• $class : (string[]) An array of additional class names added to the post.
• $post_id : (int) The post ID.

Live Example

add_filter('post_class', 'set_row_post_class', 10,3);
function set_row_post_class($classes, $class, $post_id){
    if (!is_admin()) { //make sure we are in the dashboard 
        return $classes;
    }
    $screen = get_current_screen(); //verify which page we're on
    if ('my-custom-type' != $screen->post_type && 'edit' != $screen->base) {
        return $classes;
    }
    //check if some meta field is set 
 , true);

Below is an example how you can use this hook.

                        function modify_post_class_defaults($classes, $class, $post_id) { 
   
                            // Update the $classes variable according to your website requirements and return this variable. You can modify the $classes variable conditionally too if you want.

                            return $classes; 
                        }
                        // add the filter
                        add_filter( "post_class", "modify_post_class_defaults", 10, 3 );

To remove a hook callback, use the example below.

remove_filter( "post_class", "modify_post_class_defaults", 10, 3 );

Please make sure provide the same callback function name, priority and number of arguments while removing the hook callback.

Flipper Code is a Premium WordPress Plugins development company and integrating new functionalites into WordPress sites in form of custom WordPress Plugins since 2012. If you’re having any trouble using this hook, please contact our WordPress Development Team and we’d be happy to assist you.