WordPress: get the Featured Image or fall back to the first image of a post

wordpress-post-thumbnail-or-first-image-or-default.php

function jewish_food_hero_get_best_image( $size = 'full' ) {
	$image_data = array();
	if ( has_post_thumbnail() ) {
		$image_id = get_post_thumbnail_id();
		$image_data_raw = wp_get_attachment_image_src($image_id, $size);

		$image_data['url'] = $image_data_raw[0];
		$image_data['width'] = $image_data_raw[1];
		$image_data['height'] = $image_data_raw[2];
	} else {
		global $post, $posts;
		ob_start();
		ob_end_clean();
		$output = preg_match_all( '/<img.+src=[\'"]([^\'"]+)[\'"].*>/i', $post->post_content, $matches );
		$image_data['url'] = $matches[1][0];
	}
	if ( empty( $image_data ) ) {
		$image_data = false;
	}

	return $image_data;
}

/*
 * Display Image from the_post_thumbnail or the first image of a post else display a default Image
 * Chose the size from "thumbnail", "medium", "large", "full" or your own defined size using filters.
 * USAGE: <?php echo my_image_display(); ?>
 */
function jewish_food_hero_get_best_image_url( $size = 'full' ) {
	$image_data = jewish_food_hero_get_best_image( $size );
	return $image_data['url'];
}