Probleem met Recruitment Form

<?php
if(isset($_POST['email'])) {
 
    // EDIT THE 2 LINES BELOW AS REQUIRED
    $email_to = "email verwijdert om privacy redenen";
    $email_subject = "Recruitment Form";
 
    function died($error) {
        // your error code can go here
        echo "Er zijn nog enkele fouten gevonden. ";
        echo "De fouten worden hieronder weergegeven.<br /><br />";
        echo $error."<br /><br />";
        echo "Gelieve deze fouten op te lossen en het formulier op.<br /><br />";
3        die();
    }
 
 
    // validation expected data exists
    if(!isset($_POST['naam']) ||
        !isset($_POST['straat']) ||
        !isset($_POST['stad']) ||
        !isset($_POST['postcode']) ||        
		!isset($_POST['provincie']) ||
        !isset($_POST['geslacht']) ||
        !isset($_POST['aantal']) ||        
		!isset($_POST['email']) ||
        !isset($_POST['fblink']) ||
        !isset($_POST['instalink']) ||
        !isset($_POST['subject'])) {
        died('We are sorry, but there appears to be a problem with the form you submitted.');       
    }
 
     
 
    $naam = $_POST['naam']; // required
    $straat = $_POST['straat']; // required
    $stad = $_POST['stad']; // required
    $postcode = $_POST['postcode']; // required
    $provincie = $_POST['provincie']; // required
    $geslacht = $_POST['geslacht']; // required
    $aantal = $_POST['aantal']; // required
    $email_from = $_POST['email']; // required
    $fblink = $_POST['fblink']; // not required
    $instalink = $_POST['instalink']; // not required    
	$subject = $_POST['subject']; // required

 
    $error_message = "";
    $email_exp = '/^[A-Za-z0-9._%-]+@[A-Za-z0-9.-]+\.[A-Za-z]{2,4}$/';
 
  if(!preg_match($email_exp,$email_from)) {
    $error_message .= 'Het emailadres dat u ingegeven hebt is niet correct.<br />';
  }
 
    $string_exp = "/^[A-Za-z .'-]+$/";
 
  if(!preg_match($string_exp,$naam)) {
    $error_message .= 'Geen Naam opgegeven.<br />';
  }
 
  if(!preg_match($string_exp,$straat)) {
    $error_message .= 'Geen Straat ingegeven.<br />';
  }
   if(!preg_match($string_exp,$stad)) {
    $error_message .= 'Geen Stad opgegeven.<br />';
  }
 
  if(!preg_match($string_exp,$postcode)) {
    $error_message .= 'Geen Postcode ingegeven.<br />';
  }
   if(!preg_match($string_exp,$provincie)) {
    $error_message .= 'Geen Provincie opgegeven.<br />';
  }
 
  if(!preg_match($string_exp,$email_from)) {
    $error_message .= 'Geen Email ingegeven.<br />';
  }
 
  if(strlen($subject) < 2) {
    $error_message .= 'The Comments you entered do not appear to be valid.<br />';
  }
 
  if(strlen($error_message) > 0) {
    died($error_message);
  }
 
    $email_message = "Form details below.\n\n";
 
     
    function clean_string($string) {
      $bad = array("content-type","bcc:","to:","cc:","href");
      return str_replace($bad,"",$string);
    }
 
     
 
    $email_message .= "Naam: ".clean_string($naam)."\n";
    $email_message .= "Straat: ".clean_string($straat)."\n";
    $email_message .= "Stad: ".clean_string($stad)."\n";
    $email_message .= "Postcode: ".clean_string($postcode)."\n";
    $email_message .= "Provincie: ".clean_string($provincie)."\n";
	$email_message .= "Geslacht: ".clean_string($geslacht)."\n";
    $email_message .= "Aantal keer vissen per maand: ".clean_string($aantal)."\n";
    $email_message .= "Email: ".clean_string($email_from)."\n";
    $email_message .= "fblink: ".clean_string($fblink)."\n";
    $email_message .= "instalink: ".clean_string($instalink)."\n";
    $email_message .= "Waarom wil je joinen?: ".clean_string($subject)."\n";
 
// create email headers
$headers = 'From: '.$email_from."\r\n".
'Reply-To: '.$email_from."\r\n" .
'X-Mailer: PHP/' . phpversion();
@mail($email_to, $email_subject, $email_message, $headers);  
?>
 
<!-- include your own success html here -->
 
Dank u voor uw interesse.<br>
We nemen spoedig contact met u op.

 
<?php
 
}
?>