I think the best option you have is to make an AJAX request with the values. With this you can send and assign the values to your PHP variables. 
Else you can use COOKIE etc. to store the value temporarily and then use it on server side whenever a server side function is called next.
Ajax code
<script type='text/javascript'>
    function getXMLHTTPRequest() {
    try {
    req = new XMLHttpRequest();
    } catch(err1) {
      try {
      req = new ActiveXObject("Msxml2.XMLHTTP");
      } catch (err2) {
        try {
        req = new ActiveXObject("Microsoft.XMLHTTP");
        } catch (err3) {
          req = false;
        }
      }
    }
    return req;
    }
      var http = getXMLHTTPRequest();
       function sendValue() {
    var myurl = "session.php";  // to be present in the same folder
     var myurl1 = myurl;
    var value = document.getElementById('urDIV').value;
      myRand = parseInt(Math.random()*999999999999999);
      var modurl = myurl1+"?rand="+myRand+"url"+value ; // this will set the url to be sent
      http.open("GET", modurl, true);
      http.onreadystatechange = useHttpResponse;
      http.send(null);
    }
    function useHttpResponse() {
       if (http.readyState == 4) {
        if(http.status == 200) {
          var mytext = http.responseText;
          // I dont think u will like to do any thing with the response
          // Once you get the response, you are done.
            }
         }
         else {
             // don't do anything until any result is obtained
            }
        } 
</script>
HTML Part
// considering you are calling on a button call
<input type='button' onclick='sendValue();'>