Validate_password

function validate_password($password, $min_char = 4, $max_char = 20)
{
$password = trim($password);
return $eregi = eregi('^[a-zA-Z0-9_]{'.$min_char.','.$max_char.'}$', $password);
}

if (validate_password($password)==false)
{$error[]="Wrong password";}