.repsonseText returns empty string

Question

I'm getting the following error in Chrome:

XMLHttpRequest cannot load 'http://localhost/getuser.php?q=1&sid=0.03709745453670621'. Origin null is not allowed by Access-Control-Allow-Origin.

When I click on the link 'http://localhost/getuser.php?q=1&sid=0.03709745453670621'. It displays the correct data but I don't understand why I keep getting this error and I can't figure out how to --allow-file-access-from-files.

When I run it in Firefox, I get no error but data isn't displayed either. In Javascript code, alert(xmlHttp.responseText) shows nothing which is because the responseText contains empty String. Why doesn't it contain array data?

Answer 1

The issue came up because of the same-origin policy. Adding header('Access-Control-Allow-Origin: *'); on top of my php file helped resolved the issue.