WP Post Featured Image Url Function

wp_featured_image_src.php

<?php
/**
 * WP Post Featured Image Url Function
 * @param  string $ai_post_id WP post id
 * @param  string $aa_size    WP defined image size
 * @return string             src of featured image
 */
function aa_return_img_url($ai_post_id, $aa_size) {
    $dom = simplexml_load_string(get_the_post_thumbnail($ai_post_id, $aa_size));
    $src = $dom->attributes()->src;
    return $src;
}

?>