Passing a string variable through ajax

The variable is passed through ajax and it is a database name. When the link is clicked it's supposed to retrieve a data from the the database. the link and the variable is on the same page. Here is the code for the link:

$x = strval($_GET['x']);    

echo '<a href="#" onclick="showInformation('.$x.')">'.$seatid.'</a>';

The $x variable contains the table name of the database. And here is the code for ajax:

function showInformation(str)
{
if (window.XMLHttpRequest)
  {// code for IE7+, Firefox, Chrome, Opera, Safari
  xmlhttp=new XMLHttpRequest();
  }
else
{// code for IE6, IE5
xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
}
xmlhttp.onreadystatechange=function()
{
if (xmlhttp.readyState==4 && xmlhttp.status==200)
{
document.getElementById("txtInfo").innerHTML=xmlhttp.responseText;
}
}
xmlhttp.open("GET","getinfo.php?x="+str,true);
xmlhttp.send();
}

Here is the getinfo.php:

<?php
session_start();
$_SESSION['login']="1";
$x = strval($_GET['x']);

$con = mysql_connect('localhost','root','Newpass123#','seatmapping');    
if (!$con){
    die('Could not connect: ' . mysql_error());
}

mysql_select_db('seatmapping');
$sql="SELECT name, seatid FROM $x WHERE seatid = 1";
$result = mysql_query($sql) or die("Query Error " . mysql_error());
...
...
?>

I can't get it to work when i click the link it does not display the data from the table. Please help me. Any kind of help is appreciated. Thanks in advance..