Validate form with PHP and Regular Expressions

script.php

<?php

// Presence check
if ($firstname == '' || $lastname == '' || $street == '' || $suburb == '' || $postcode == '' || $email == '' || $status == '' || $dob == '') {
  $error = 'Your field is empty';
  renderForm($firstname, $lastname, $street, $suburb, $postcode, $email, $status, $dob, $error);
// Validate Email
} elseif (ereg('\S+@\S+\.\S+', $email) == false)  {
  $error = 'Please enter a valid email address.';
  renderForm($firstname, $lastname, $street, $suburb, $postcode, $email, $status, $dob, $error);
// Validate Postcode
} elseif (ereg('^[0-9]{4}$', $postcode) == false) {
  $error = 'Only 4 digit postcodes are accepted.';
  renderForm($firstname, $lastname, $street, $suburb, $postcode, $email, $status, $dob, $error);
// Validate Date of Birth
} elseif (ereg('^([0-9]{2})\/([0-9]{2})\/([0-9]{4})$', $dob) == false) {
  $error = 'Your birthday must be in the form of DD/MM/YYYY.';
  renderForm($firstname, $lastname, $street, $suburb, $postcode, $email, $status, $dob, $error);
} else {
  ...
}

?>

Lol @ how you have to use <?php ?> to start a php script. Forgot about that.