How to use post_thumbnail_html filter in WordPress

post_thumbnail_html filter

Filters the post thumbnail HTML.

    apply_filters( 'post_thumbnail_html', string $html, int $post_id, int $post_thumbnail_id, string|int[] $size, string|array $attr )
    

Description

This is a filter hook, and it filters the HTML of the post thumbnail. It is used for rewriting the HTML output for post thumbnails.

Parameters

• $html: (string) The post thumbnail HTML.
• $post_id: (int) The post ID.
• $post_thumbnail_id: (int) The post thumbnail ID, or 0 if there isn’t one.
• $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).
• $attr: (string|array) Query string or array of attributes.

Live Examples

Example 1: Basic Usage

To run the hook, you can copy the example below:

    $html = apply_filters( 'post_thumbnail_html', $html, $post_id, $post_thumbnail_id, $size, $attr ); 
                             
    if ( !empty( $html ) ) { 
                             
       // everything has led up to this point... 
                             
    } 
    

Example 2: Adding a Hook Callback

The following example is for adding a hook callback:

    // define the post_thumbnail_html callback 
    function weplugins_filter_post_thumbnail_html( $html, $post_id, $post_thumbnail_id, $size, $attr ) { 
        // make filter magic happen here... 
        return $html; 
    }; 
             
    // add the filter 
    add_filter( 'post_thumbnail_html', 'weplugins_filter_post_thumbnail_html', 10, 5 );  
    

Example 3: Removing a Hook Callback

To remove a hook callback, use the example below:

    // remove the filter 
    remove_filter( 'post_thumbnail_html', 'weplugins_filter_post_thumbnail_html', 10, 5 ); 
    

Example 4: Adding Title Attribute to Thumbnail

If you want to add a title attribute to the post thumbnail, use the following code:

    function weplugins_addTitleToThumbnail( $html ) {
        $id = get_post_thumbnail_id();
        $alt_text = get_post_meta( $id, '_wp_attachment_image_alt', true );
         $html = str_replace( 'alt=', 'title="' . esc_attr( $alt_text ) . '" alt=', $html );
         return $html;
    }
    add_filter( 'post_thumbnail_html', 'weplugins_addTitleToThumbnail' );