Retrieves the amount of comments a post has.

function get_comments_number( $post = 0 ) {
	$post = get_post( $post );

	$count   = $post ? $post->comment_count : 0;
	$post_id = $post ? $post->ID : 0;

	/**
	 * Filters the returned comment count for a post.
	 *
	 * @since 1.5.0
	 *
	 * @param string|int $count   A string representing the number of comments a post has, otherwise 0.
	 * @param int        $post_id Post ID.
	 */
	return apply_filters( 'get_comments_number', $count, $post_id );
}