xmlHTTPRequest POST not sending data - php

Question

I had xmlHTTPrequest GET script which was working fine, but because of server issues I had to change it to POST method. I am unable to get the data in $_POST variable. When I checked in CHROME INSPECTOR debug tool, GET Method status is 200 ok. Need help to see if the javascript is correct.
xmlHTTPrequest file:
<script type="text/javascript">
function showprodes(str2)
{
var q2 = encodeURIComponent(str2);
if (window.XMLHttpRequest)
{// code for IE7+, Firefox, Chrome, Opera, Safari
xmlhttp=new XMLHttpRequest();
}
else
{// code for IE6, IE5
xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
}
var url = "http://www.amg.in/amogtst/rateprod.php";
xmlhttp.open("POST", url, true);
xmlhttp.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
xmlhttp.send(q2);
}
</script>
<?
$result2 = mysql_query("SELECT Prod_desc FROM PRODMAST ORDER BY Prod_desc");
echo "<form name='f1'>";
echo " <span class='style3'>Gas Type </span> <select name='Proddesc' onchange=\"showprodes(this.value);\"><option value=0>Select a Product</option>";
while($nt2=mysql_fetch_assoc($result2))
{
echo "<option value='$nt2[Prod_desc]'>$nt2[Prod_desc]</option>";
}
echo "</select>";// Closing of list box
echo "</form>";
?>
Second script which updates the table as per the user selection from first php: rateprod.php file:
<?php
$q=$_POST['q2'];
$q2=mysql_real_escape_string($q);
include_once 'db.php';
mysql_query("UPDATE RATEMASTER_draft SET Prod_desc='$q2'");
?>

Answer 1

From looking at your AJAX code, you aren't supplying the POST variables correctly. The format for the POST string being given to xmlhttp.send() needs to be in the same format as a GET string. Trying using xmlhttp.send("q2=" + q2).
BTW, for future reference, you can use print_r($_POST) to show the contents of all POST variables. This can be very handy for debugging.