Friday, 31 August 2018

ajax php call does not return anything

I want php to return a value to ajax. I'm following W3 schools example but no joy. Here is the javascript/ajax code:

function createReport() {
    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) {
            document.getElementById("report").innerHTML=xmlhttp.responseText;
        }
    }
    xmlhttp.open("GET","test.php",true);
    xmlhttp.send();
}
I have the following call inside an event handler that I know is triggering (other stuff it does is working fine)
createReport();
and later in the body section of the html I have:
<div id="report">Report will be placed here...</div>
If I run test.php by itself, it correctly shows "return this to ajax" so I know that's working. Here is the php code:
<?php
echo 'return this to ajax';
?>
My understanding is that "Report will be placed here..." will be replaced with "return this to ajax". But nothing happens. I don't see any errors listed in the firefox or IE consoles either. Any ideas?
I did not find anything wrong with W3Schools' Ajax example, after testing the code that follows (which was pulled from their Website).
  • Possible factors:
    1. Missing <script></script> tags
    2. Make sure you have JS enabled.
    3. Make sure your browser supports it.
    4. You may have forgotten to change the button's call to the proper function.

Working and tested code using FF 26.0 and IE version 7

Pulled from W3 Schools Website (example) and slightly modified to prove this works.
Result when clicking on the Change Content button:
return this to ajax - as per your PHP code.
<!DOCTYPE html>
<html>
<head>
<script>
function loadXMLDoc()
{
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)
    {
    document.getElementById("report").innerHTML=xmlhttp.responseText;
    }
  }
xmlhttp.open("GET","test.php",true);
xmlhttp.send();
}
</script>
</head>
<body>

<div id="report"><h2>Let AJAX change this text</h2></div>
<button type="button" onclick="loadXMLDoc()">Change Content</button>

</body>
</html>
PHP used: (test.php)
<?php
echo 'return this to ajax';
?>
  • Other possible factors:
    1. If on a local machine, your server doesn't support PHP or is not parsing PHP properly, or is either not installed or configured properly.
    2. If on a hosted service, make sure PHP is available for you to use.
    3. Files are not in the same folder as executed from.

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