เรียนถามท่านผู้รู้ php รับ email แล้วเป็นภาษาต่างด้าวต้องแก้ยังไง

  <script type="text/javascript">
function checkForm()
{
	var tmail =document.getElementById('tmail');	
	var header =document.getElementById('header');
	var subject =document.getElementById('subject');
	var detail =document.getElementById('detail');


if (tname.value=='')
	{
		alert('กรุณา กรอกชื่อ-นามสกุล');
		tname.focus();
		return false;
	
	}

	if (header.value=='')
	{
		alert('กรุณา กรอกอีเมลผู้ส่ง');
		header.focus();
		return false;
	
	}
		
	if (subject.value=='')
	{
		alert('กรุณา กรอกเรื่องที่ต้องการติดต่อ');
		subject.focus();
		return false;
	
	}
	if (detail.value=='')
	{
		alert('กรุณา กรอกรายละเอียด');
		detail.focus();
		return false;
	
	}
	
}
</script>
      <form onSubmit="return checkForm();" name="form1" method="post" action="send_mail.php">
       <table width="600" border="0" cellspacing="0" cellpadding="0">
  <tr>
    <td width="122" height="28">&nbsp;</td>
    <td width="375"><font size="2">ฝากข้อความ&nbsp;</font></td>
  </tr>
  <tr>
    <td><font size="3">ชื่อ-นามสกุล *</font></td>
    <td> <input name="tname" type="text" id="tname" size="50"></td>
  </tr>
  <tr>
    <td><font size="3">เบอร์โทร</font></td>
    <td><input name="tel" type="text" id="tel" size="50"></td>
  </tr>
  <tr>
    <td><font size="3">อีเมลผู้ส่ง *</font></td>
    <td>
      <input name="header" type="text" id="header" size="50">
   </td>
  </tr>
  <tr>
    <td><font size="3">เรื่องที่ต้องการติดต่อ *</font></td>
    <td>
      <input name="subject" type="text" id="subject" size="50">
    </td>
  </tr>
  <tr>
    <td><font size="3">รายละเอียด *</font></td>
    <td>
      <textarea name="detail" id="detail" cols="50" rows="6"></textarea>
   </td>
  </tr>
  <tr>
    <td>
      &nbsp;&nbsp;&nbsp;&nbsp;<input type="submit" name="submit" id="submit" value="ส่งเมล">
   </td>
    <td>&nbsp;</td>
  </tr>
</table>

      </form>

<meta http-equiv="Content-Type" content="text/html;charset=utf-8" /><title>Send Mail</title>
<?php 
if(isset($_POST['header'])) { 
$email_to = "[email protected]"; 
  function died($error) {              
 		 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("<script>alert('กรอกอีเมลผู้ส่งผิดรูปแบบ');history.back();</script>");   
		
	} 
  
  if(!isset($_POST['tname']) || 
    !isset($_POST['tel']) || 
  	!isset($_POST['header']) ||    
	!isset($_POST['subject']) ||        
	!isset($_POST['detail'])) {      
  died('We are sorry, but there appears to be a problem with the form you submitted.');          
  } 
  $tname ->tname = iconv("tis-620","utf-8",$_POST['tname']); 
   $tel ->tel = iconv("tis-620","utf-8",$_POST['tel']);
   $header ->header = iconv("tis-620","utf-8",$_POST['header']); 
   $subject ->subject = iconv("tis-620","utf-8",$_POST['subject']);
   $detail ->detail = iconv("tis-620","utf-8",$_POST['detail']);  
    $error_message = ""; 
    $email_exp = '/^[A-Za-z0-9._%-]+@[A-Za-z0-9.-]+\.[A-Za-z]{2,4}$/'; 
  if(!preg_match($email_exp,$header)) { 
    $error_message .= 'The Email Address 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);   
	  } 
      $email_message .= "Name: ".clean_string($tname)."\n";     
	  $email_message .= "Tel: ".clean_string($tel)."\n";  
	  $email_message .= "Email: ".clean_string($header)."\n";     
	  $email_message .= "Subject: ".clean_string($subject)."\n";     
	  $email_message .= "Detail: ".clean_string($detail)."\n";      
	  ini_set("SMTP","smtpweb.netdesignhost.com"); 
	  $headers = 'From: '.$header."\r\n". 
	  'Reply-To: '.$header."\r\n" . 
	  'X-Mailer: PHP/' . phpversion(); 
	  mail($email_to, $subject, $email_message, $headers);   
}


echo"<script>window.location='index.php';</script>";

?>