title: Verifying XMLHttpRequest in php
body: <p>I am sending data to a PHP site using the following code:</p>
  
  <pre><code>if (window.XMLHttpRequest)
        {// code for IE7+, Firefox, Chrome, Opera, Safari
                xmlhttp= new XMLHttpRequest();
        }
        else
        {// code for IE6, IE5
            xmlhttp= new ActiveXObject("Microsoft.XMLHTTP");
        }
        xmlhttp.open("GET","addEmail.php?email="+escape(email),true);
        xmlhttp.send();
        xmlhttp.close;
  </code></pre>
  
  <p>Is there any way of making sure that the <code>addEmail.php</code> is being run through the <code>XMLHttpRequest</code> so people cant simply go to <code>www.domain.com/addEmail.php?email=some@thing.com</code> to make the php site eat their email and run a thousand requests on the page? Thanks in advance</p>