function get_the_post_thumbnail( $post = null, $size = 'post-thumbnail', $attr = '' ) {
  $post = get_post( $post );

  if ( ! $post ) {
    return '';
  }

  $post_thumbnail_id = get_post_thumbnail_id( $post );

  
/**
 * Filters the post thumbnail size.
 *
 * @since 2.9.0
 * @since 4.9.0 Added the `$post_id` parameter.
 *
 * @param string|int[] $size    Requested image size. Can be any registered image size name, or
 *                              an array of width and height values in pixels (in that order).
 * @param int          $post_id The post ID.
 */
  $size = apply_filters( 'post_thumbnail_size', $size, $post->ID );

  if ( $post_thumbnail_id ) {

    
/**
 * Fires before fetching the post thumbnail HTML.
 *
 * Provides "just in time" filtering of all filters in wp_get_attachment_image().
 *
 * @since 2.9.0
 *
 * @param int          $post_id           The post ID.
 * @param int          $post_thumbnail_id The post thumbnail ID.
 * @param string|int[] $size              Requested image size. Can be any registered image size name, or
 *                                        an array of width and height values in pixels (in that order).
 */
    do_action( 'begin_fetch_post_thumbnail_html', $post->ID, $post_thumbnail_id, $size );

    if ( in_the_loop() ) {
      update_post_thumbnail_cache();
    }

    $html = wp_get_attachment_image( $post_thumbnail_id, $size, false, $attr );

    
/**
 * Fires after fetching the post thumbnail HTML.
 *
 * @since 2.9.0
 *
 * @param int          $post_id           The post ID.
 * @param int          $post_thumbnail_id The post thumbnail ID.
 * @param string|int[] $size              Requested image size. Can be any registered image size name, or
 *                                        an array of width and height values in pixels (in that order).
 */
    do_action( 'end_fetch_post_thumbnail_html', $post->ID, $post_thumbnail_id, $size );

  } else {
    $html = '';
  }

  
/**
 * Filters the post thumbnail HTML.
 *
 * @since 2.9.0
 *
 * @param string       $html              The post thumbnail HTML.
 * @param int          $post_id           The post ID.
 * @param int          $post_thumbnail_id The post thumbnail ID, or 0 if there isn't one.
 * @param string|int[] $size              Requested image size. Can be any registered image size name, or
 *                                        an array of width and height values in pixels (in that order).
 * @param string|array $attr              Query string or array of attributes.
 */
  return apply_filters( 'post_thumbnail_html', $html, $post->ID, $post_thumbnail_id, $size, $attr );
}