Free Online Tutorials

<form action="http://cdn.tutorialspots.com/ajax.php?action=uploadimage" method="POST" enctype="multipart/form-data" class="dropzone needsclick dz-clickable dz-started" id="demo-upload">
     ...
</form>

We upload to other domain (cdn.tutorialspots.com), we see a request with method OPTIONS

We see a request header:

Access-Control-Request-Headers: cache-control,x-requested-with

and don’t see response header Access-Control-Allow-Headers

This is the reason why we get this error.

Code to fix this error:

<?php 
header('Access-Control-Allow-Origin: *');
header('Access-Control-Allow-Methods: PUT, GET, POST, DELETE, OPTIONS'); 

if(array_key_exists('HTTP_ACCESS_CONTROL_REQUEST_HEADERS', $_SERVER)) {
    header('Access-Control-Allow-Headers: '
           . $_SERVER['HTTP_ACCESS_CONTROL_REQUEST_HEADERS']);
} else {
    header('Access-Control-Allow-Headers: origin, x-requested-with, content-type, cache-control');
}

if($_SERVER['REQUEST_METHOD']=='OPTIONS') die();