php - check IP address validity

/*
Is IPAdress valid

Checks if a IP adress has a valid format
*/
// Sorry, currently I did not make a routine for IPv6,
// but I'm sure you find one at: http://regexlib.com/

function IsIPValid($ip){

    if (preg_match('/^[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}$/', $ip)){
        return true;
    }

    return false;
}