简化php表单验证-将两个文件合并为一个文件

我的php和javascript知识有限。我正在上课：）

我有一个表单，它检查字段是否为空；如果是，则会出现警报。然后，第二个php文件检查提交的表单，以查看电子邮件和电话号码是否符合参数；如果没有，则不提交表单，并在新页面上显示错误。有办法把两者结合起来吗？

这是contact.php上的代码：

<script>
    function validateForm()
    {
    var x=document.forms["contactform"]["companyname"].value;
    var y=document.forms["contactform"]["name"].value;
    var z=document.forms["contactform"]["telephone"].value;
    var e=document.forms["contactform"]["email"].value;
    if (x==null || x=="")
      {
      alert("company name must be filled out");
      return false;
      }
      if (y==null || y=="")
      {
      alert("name must be filled out");
      return false;
      }
      if (z==null || z=="")
      {
      alert("telephone must be filled out");
      return false;
      }
      if (e==null || e=="") 
      {
      alert("email must be filled out");
      return false;
      }
    //send
    alert("Form sent."); 
    document.contactform.submit();  
    }
  </script>

在第二个send_form_email.php中：

    function died($error) {
        // your error code can go here
        echo "We are very sorry, but there were error(s) found with the form you submitted. ";
        echo "These errors appear below.<br /><br />";
        echo $error."<br /><br />";
        echo "Please go back and fix these errors.<br /><br />";
        die();
    }
    // validation expected data exists
    if(
        !isset($_POST['telephone']) ||
        !isset($_POST['email'])) 
        {
        died('We are sorry, but there appears to be a problem with the form you submitted.');       
    }
    $companyname = $_POST['companyname']; // required
    $name = $_POST['name']; // required
    $telephone = $_POST['telephone']; // required
    $email_from = $_POST['email']; // required
    $comments = $_POST['comments']; // not 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 />';
  }
   $string_exp = "/^[0-9.'-]+$/";

  if(!preg_match($string_exp,$telephone)) {
    $error_message .= 'The Phone Number you entered does not appear to be valid.<br />';
  }
  if(strlen($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);
    }