Question

This is my code for an XMLHttpRequest to get data from a PHP page. When I alert the variable user_data inside an “if” it works. But below all of this code the variable doesn’t exist any more.

Thanks for the help!

    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)
    {
    user_data = xmlhttp.responseText;
    alert (user_data); //THIS WORKS
    }
  }
xmlhttp.open("GET","http://myurl.com/index.php",true);
xmlhttp.send();
alert (user_data); //THIS DOESN'T WORK

Answer 1

It’s an asynchronous request. The non-working alert is executed before the request returns. The variable isn’t assigned until the request completes.