Subzero | Append topicId to first link

<?php
	@session_start();
	if (isset($_GET["topic"]))
	{
		$_SESSION["topic"] = $_GET["topic"];
	}
?>
<script>
$(document).ready(function() {
	var QueryString = function () {
	  // This function is anonymous, is executed immediately and
	  // the return value is assigned to QueryString!
	  var query_string = {};
	  var query = window.location.search.substring(1);
	  var vars = query.split("&");
	  for (var i=0;i<vars.length;i++) {
		var pair = vars[i].split("=");
			// If first entry with this name
		if (typeof query_string[pair[0]] === "undefined") {
		  query_string[pair[0]] = decodeURIComponent(pair[1]);
			// If second entry with this name
		} else if (typeof query_string[pair[0]] === "string") {
		  var arr = [ query_string[pair[0]],decodeURIComponent(pair[1]) ];
		  query_string[pair[0]] = arr;
			// If third or later entry with this name
		} else {
		  query_string[pair[0]].push(decodeURIComponent(pair[1]));
		}
	  }
	  return query_string;
	}();

	var topicId = parseInt(QueryString.topic);

	var linktxt = $(".body_message .body_content .post").find("a").first().attr("href");
	linktxt = linktxt.split("index.php?");
	if (linktxt[1]!=undefined)
	{
		linktxt = linktxt[0]+"index.php?topic="+topicId+"&"+linktxt[1];
		$(".body_message .body_content .post").find("a").first().attr("href",linktxt);
	}
});
</script>