Add a phone number to the listing url

This snippet will alter the listing URL to include phone number of the listing:  www.site.com/listings/3331542847/listing-name/

In your child theme functions.php file add this code.

function listing_post_type_link($permalink, $post)
{
	// Abort if post is not a listing
	if ($post->post_type !== 'listing')
		return $permalink;

	// Abort early if the placeholder rewrite tag isn't in the generated URL
	if (false === strpos($permalink, '%'))
		return $permalink;

	$find = array(
		'%phone%'
	);
$phone = get_post_meta($post->ID,'_phone',true);
	$replace = array(
		$phone
	);

	$replace = array_map('sanitize_title', $replace);

	$permalink = str_replace($find, $replace, $permalink);

	return $permalink;
}
add_filter('post_type_link', 'listing_post_type_link', 10, 2);

function change_listing_slug($args)
{
	$args['rewrite']['slug'] = 'listing/%phone%';
	return $args;
}
add_filter('register_post_type_listing', 'change_listing_slug');

After that go to Settings -> Permalinks, and click Save to renew new permalinks