Question

I have a AJAX script which sends a POST request to PHP with some values. When I try to retrieve the values in PHP, am not able to get anything.

The AJAX script is

xmlhttp.open("POST","handle_data.php",true);
xmlhttp.setRequestHeader("Content-type","text/plain");
var cmdStr="cmd1=Commanda&cmd2=Command2";
xmlhttp.send(cmdStr);
alert(xmlhttp.responseText); 

The PHP script is

<?php
  echo $_POST['cmd1'];
?>

The output is just a plain empty alert box. Is there any mistake in the code?

Answer 1

xmlhttp.onreadystatechange = function()
{
    if(this.readyState == 4 && this.status == 200)
    {
        if(this.responseText != null)
        {
            alert(this.responseText);
        }
    };
}

You need to wait for the data to be received, use the onreadystatechange to delegate a callback.

http://www.w3.org/TR/XMLHttpRequest/