I wrote a code for login verification..I got output with GET. But i need output with POST since it is more secure.pls let me know if there is any error in my code.

javascript code:

var xml;
function verifyusernamepasswd(pass)
{
//pass is password that will be passed as parameter
xml=new XMLHttpRequest();
var url="http://localhost/loginvalidate.php";
var para="q="+username+"&p="+pass;//username is global
xml.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
xml.setRequestHeader("Content-length", para.length);
xml.setRequestHeader("Connection", "close");
xml.open("POST",url,true);
xml.onreadystatechange=statechanged1;
xml.send(para);

}

function statechanged1()
{
if(xml.readyState==4)
alert(xml.responseText);

}


php code:

<?php
$username=$_POST["q"];
$password=$_POST["p"];
$con=mysql_connect("localhost","root","blaze");
if(!$con)
{
die('Could not connect: '.mysql.error());
}
mysql_select_db("BLAZE",$con) or die("No such Db");
$result=mysql_query("SELECT Passwword FROM USERTABLE WHERE Userhandle='$username'");
if($result==null)
echo "false";

else if($result!=null)
{
$row=mysql_fetch_array($result);
if((strcmp($row['Passwword'],$password)==0))
echo "true";
else
echo "false";
}

?>

the verification does not return anything, cos my alert is not displayed at all...pls tell me whats wrong....