PHP Referrer not detect if redirect from another domain using .htaccess

Hi,

I need an assistant.

i made 301 redirection using .htaccess to new domain name as follows :

#REDIRECT TO IWHOST

RewriteCond %{HTTP_HOST} ^domain.com [NC,OR]
RewriteCond %{HTTP_HOST} ^www.domain.com [NC]
RewriteCond %{REQUEST_URI} !/(fpx_indirectcallback|fpx_directcallback|molpay_callback|paypal|billplzBills)\.php [NC]
RewriteRule ^(.*)$ https://iwhost.com/$1 [L,R=301,NC]

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and at the iwhost.com i made a php script in index.php as follows :

// Check referrer

$ref = $_SERVER['HTTP_REFERER'];

$refData = parse_url($ref);

if($refData['host'] == 'domain.com' || $refData['host'] == 'www.domain.com'  ) {

echo "<link rel='stylesheet' href='css/swc.css'>
<div id='boxespopup'>
  <div style='top: 50%; left: 50%; display: none;' id='dialog' class='window'>
    <div id='san'>
      <a href='#' class='close agree'><img src='img/close-icon.png' width='25' style='float:right; margin-right: -25px; margin-top: -20px;'></a>
      <img src='img/notice.jpg'>
    </div>
  </div>
    <div style='width: 2478px; font-size: 32pt; color:white; height: 1202px; display: none; opacity: 0.4;' id='mask'></div>
</div>
<script src='https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.js'></script>
<script src='js/swc.js'></script>";
}

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The problem is that why iwhost receive empty referrer when redirect using the above method.

Please advice alternate method or idea on how to achieve my requirement.