Not retriving databse values using ajax

function showUser(str)
{
if (str=="")
  {
  document.getElementById("txtHint").innerHTML="";
  return;
  }
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("txtHint").innerHTML=xmlhttp.responseText;
    }
  }
xmlhttp.open("GET","systemdate.php?inputField="+str,true);
xmlhttp.send();
};
</script>

<?php
$inputField=$_GET['inputField'];
$res1="SELECT DISTINCT time FROM import WHERE date1='".$inputField."'";
while($row=mysql_fetch_assoc($res1))
 {
echo "<option value=$row[time]>$row[time]</option>";
}
echo "</select>";
?>