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";}

PHP validate email

function isValidEmail($email){
return eregi("^[_a-z0-9-]+(\.[_a-z0-9-]+)*@[a-z0-9-]+(\.[a-z0-9-]+)*(\.[a-z]{2,3})$", $email);
}

$email=mysql_real_escape_string($_POST['email']);
if (isValidEmail($email)==true) echo "OK";
if (isValidEmail($email)==false) echo "Not Okay";
?>