How can I set up a PHP form to validate content before deciding to send as an email

What I like to do is have an integer based "error" variable that starts at 0. In the event that something does not get validated, I change that variable to a 0. If the error variable equals 0 after the validation, I know that everything is valid and I can send mail.

For some reason, WF isn't allowing me to place this in [code ] or [php ] tags.

function checkName($string) {
return preg_match('my regexp here', $string);
}

function checkPhone($string) {
return preg_match('my regexp here', $string);
}

function checkEmail($string) {
return preg_match('my regexp here', $string);
}

if (isset($_POST['name']) &&
isset($_POST['phone']) &&
isset($_POST['email'])) {

$name = $_POST['name'];
$phone = $_POST['phone'];
$email = $_POST['email'];

$error = 0;

if (!checkName($name) ||
!checkPhone($phone) ||
!checkEmail($email)) $error = 1;

if ($error == 0) {
mail('you@example.com','bla','bla','bla');
die ('Thank-you for your feedback.');
} else {
die('An error has occurred. Make sure you entered valid information.');
}

} else {

die('Please fill in all fields.');

}

Or you could just have the PHP call up an HTML form that validates.

And I am thinking that maaaaybe you could have an HTML form that validates via variables defined elsewhere