TBN: caption transfer

gistfile1.php

function tbn_update_featured_image_captions() {
	$caption_counter = 1;
		
	$is_done = get_transient( '_breakingnews_caption_transfer' );
	
	if ( $is_done ) {
		echo '<h2>==> The update process is already done <==</h2>';
		
		return;
	}
	
	for ($page = 1; $page <= 3; $page++) {
    	$args = array(
			'post_type' => 'post',
			'meta_key' => '_td_featured_image_credits',
			'posts_per_page' => 1000,
			'paged' => $page,
		);

		$custom_query = new WP_Query( $args );
		
		while ( $custom_query->have_posts() ) : $custom_query->the_post();
			if ( has_post_thumbnail() && get_post_thumbnail_id( get_the_ID() ) ) {
				$old_caption = get_post_meta( get_the_ID(), '_td_featured_image_credits', true );
				
				wp_update_post(
					array(
						'ID' => get_post_thumbnail_id( get_the_ID() ),
						'post_excerpt' => $old_caption,
					)
				);

				echo $caption_counter . '--> "'.  $old_caption .'" has been updated. <br>';

				$caption_counter++;
			}

		endwhile;
		
		wp_reset_postdata();
	}
	
	set_transient( '_breakingnews_caption_transfer', true, 14400 );
}
add_action( 'wp_footer', 'tbn_update_featured_image_captions' );