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How to use admin_post_thumbnail_size filter in WordPress

Sandeep Kumar Mishra
Sandeep Kumar Mishra
August 3, 2022
5 minutes read

admin_post_thumbnail_size filter

Note: When a theme adds ‘post-thumbnail’ support, a special ‘post-thumbnail’ image size is registered, which differs from the ‘thumbnail’ image size managed via the Settings > Media screen.

To use admin_post_thumbnail_size 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 WePlugins 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 weplugins_modify_admin_post_thumbnail_size_defaults which takes 3 parameters and we registered using add_filter. The first parameter admin_post_thumbnail_size is the name of the hook, the second parameter weplugins_modify_admin_post_thumbnail_size_defaults is the name of the function which needs to be called, the third parameter is the priority of calling the hook if the same hook is used multiple times and the last parameter is the number of arguments (if any) to be passed in the registered function.

Sometimes, you have to remove a registered hook so you can use remove_filter to remove admin_post_thumbnail_size filter.

Parameters

    Below are the 3 parameters required to use this hook.

  • $size: (string|int[]) Requested image size. Can be any registered image size name, or an array of width and height values in pixels (in that order).
  • $thumbnail_id: (int) Post thumbnail attachment ID.
  • $post: (WP_Post) The post object associated with the thumbnail.

Live Examples

Example 1: Basic Usage

Below is an example of how you can use this hook to modify the post thumbnail size.

    function weplugins_modify_admin_post_thumbnail_size_defaults($size, $thumbnail_id, $post) { 
        // Update the $size variable according to your website requirements and return this variable. You can modify the $size variable conditionally too if you want.
        return $size; 
    }
    // add the filter
    add_filter( "admin_post_thumbnail_size", "weplugins_modify_admin_post_thumbnail_size_defaults", 10, 3 );
    

Example 2: Conditional Size Adjustment

In this example, we conditionally adjust the post thumbnail size based on the post type.

    function weplugins_modify_admin_post_thumbnail_size_conditionally($size, $thumbnail_id, $post) { 
        if ($post->post_type == 'custom_type') {
            $size = array(300, 300); // Custom size for custom post type
        }
        return $size; 
    }
    // add the filter
    add_filter( "admin_post_thumbnail_size", "weplugins_modify_admin_post_thumbnail_size_conditionally", 10, 3 );
    

Example 3: Removing the Hook

To remove a hook callback, use the example below.

    // remove the filter
    remove_filter( "admin_post_thumbnail_size", "weplugins_modify_admin_post_thumbnail_size_defaults", 10, 3 );
    

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

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Contact Us

If you need any customization or are having trouble using this hook, please contact us and we’d be happy to assist you.

Sandeep Kumar Mishra

Sandeep Kumar Mishra

Sandeep Kumar Mishra writes about WordPress and Artificial Intelligence, offering tips and guides to help you master your website and stay updated with the latest tech trends.

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