Using WordPress ‘end_fetch_post_thumbnail_html’ PHP action

by

The end_fetch_post_thumbnail_html WordPress action fires after fetching the post thumbnail HTML.

Usage

add_action('end_fetch_post_thumbnail_html', 'your_custom_function', 10, 3);

function your_custom_function($post_id, $post_thumbnail_id, $size) {
    // your custom code here
}

Parameters

  • $post_id (int): The post ID.
  • $post_thumbnail_id (int): The post thumbnail ID.
  • $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).

More information

See WordPress Developer Resources: end_fetch_post_thumbnail_html

Examples

Add a watermark to post thumbnail

Add a watermark to the post thumbnail after it’s fetched.

add_action('end_fetch_post_thumbnail_html', 'add_watermark_to_thumbnail', 10, 3);

function add_watermark_to_thumbnail($post_id, $post_thumbnail_id, $size) {
    // Get the image source
    $image_src = wp_get_attachment_image_src($post_thumbnail_id, $size);

    // Add watermark to the image
    $watermarked_image_src = add_watermark($image_src[0]);

    // Replace the original image src with the watermarked image src
    echo str_replace($image_src[0], $watermarked_image_src, get_the_post_thumbnail($post_id, $size));
}

Add custom CSS class to post thumbnail

Add a custom CSS class to the post thumbnail HTML.

add_action('end_fetch_post_thumbnail_html', 'add_custom_css_class_to_thumbnail', 10, 3);

function add_custom_css_class_to_thumbnail($post_id, $post_thumbnail_id, $size) {
    // Add custom CSS class to the thumbnail
    $class = 'custom-thumbnail-class';
    echo str_replace('class="', 'class="' . $class . ' ', get_the_post_thumbnail($post_id, $size));
}

Add data attribute to post thumbnail

Add a data attribute to the post thumbnail HTML.

add_action('end_fetch_post_thumbnail_html', 'add_data_attribute_to_thumbnail', 10, 3);

function add_data_attribute_to_thumbnail($post_id, $post_thumbnail_id, $size) {
    // Add data attribute to the thumbnail
    $data_attribute = 'data-custom="example"';
    echo str_replace('<img', '<img ' . $data_attribute, get_the_post_thumbnail($post_id, $size));
}

Add lazy loading to post thumbnails

Add lazy loading attribute to post thumbnails.

add_action('end_fetch_post_thumbnail_html', 'add_lazy_loading_to_thumbnail', 10, 3);

function add_lazy_loading_to_thumbnail($post_id, $post_thumbnail_id, $size) {
    // Add lazy loading attribute to the thumbnail
    echo str_replace('<img', '<img loading="lazy"', get_the_post_thumbnail($post_id, $size));
}

Add image dimensions to the post thumbnail

Add width and height attributes to the post thumbnail.

add_action('end_fetch_post_thumbnail_html', 'add_dimensions_to_thumbnail', 10, 3);

function add_dimensions_to_thumbnail($post_id, $post_thumbnail_id, $size) {
    // Get the image dimensions
    $image_src = wp_get_attachment_image_src($post_thumbnail_id, $size);
    $width = $image_src[1];
    $height = $image_src[2];

    // Add width and height attributes to the thumbnail
    $thumbnail_html = get_the_post_thumbnail($post_id, $size);
    $thumbnail_html = str_replace('<img', '<img width="' . $width . '" height="' . $height . '"', $thumbnail_html);
    echo $thumbnail_html;
}