Validate URL hostname

validate_hostname.php

/**
 * Validate host name
 *
 * @link http://stackoverflow.com/questions/1755144/how-to-validate-domain-name-in-php
 * @param  string $host
 * @return bool
 */
function  isValidHostName($host)
{
	return (preg_match("/^([a-z\d](-*[a-z\d])*)(\.([a-z\d](-*[a-z\d])*))*$/i", $host) //valid chars check
		&& preg_match("/^.{1,253}$/", $host) //overall length check
		&& preg_match("/^[^\.]{1,63}(\.[^\.]{1,63})*$/", $host) //length of each label
		&& !filter_var($host, FILTER_VALIDATE_IP)); //is not an IP address
}