html - Detect click on via PHP

if x.php is the handling php file then do this:

here's javascript:

function doThis()
{
var xmlhttp;
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)
    {
    //do whatever you want upon getting response from php file
    }
  }
xmlhttp.open("GET","x.php",true); //call PHP file on click
xmlhttp.send();
}