메일폼에 이메일 메세지는 4가지 이상 못하나요?

// validation expected data exists
    if(!isset($_POST['first_name']) ||
        !isset($_POST['email']) ||
        !isset($_POST['telephone']) ||
 

        !isset($_POST['comments'])){
        died('We are sorry, but there appears to be a problem with the form you submitted.');      
    }
    
    $first_name = $_POST['first_name']; // required
    $email_from = $_POST['email']; // required
    $telephone = $_POST['telephone']; // not required
 


    $comments = $_POST['comments']; // 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 .= 'The Email Address you entered does not appear to be valid.<br />';
  }
   
  if(strlen($comments) < 2) {
    $error_message .= 'The Comments you entered do not appear to be valid.<br />';
  }
  if(strlen($error_message) > 0) {
    died($error_message);
  }
    $email_message = "";
    
    function clean_string($string) {
      $bad = array("content-type","bcc:","to:","cc:","href");
      return str_replace($bad,"",$string);
    }
    
    $email_message .= "이름 : ".clean_string($first_name)."\n\n";
    $email_message .= "이메일 : ".clean_string($email_from)."\n\n";
    $email_message .= "연락처 : ".clean_string($telephone)."\n\n";
 
    $email_message .= "주소 및 수거날짜 : ".clean_string($comments)."\n\n";