Cross-Origin Request Headers(CORS) with PHP headers

Access-Control-Allow-Headers does not allow * as accepted value, see the Mozilla Documentation here.

Instead of the asterisk, you should send the accepted headers (first X-Requested-With as the error says).

Update:

* is now accepted is Access-Control-Allow-Headers.

According to MDN Web Docs 2021:

The value * only counts as a special wildcard value for requests without credentials (requests without HTTP cookies or HTTP authentication information). In requests with credentials, it is treated as the literal header name * without special semantics. Note that the Authorization header can't be wildcarded and always needs to be listed explicitly.

Many description internet-wide don't mention that specifying Access-Control-Allow-Origin is not enough. Here is a complete example that works for me:

<?php
    if ($_SERVER['REQUEST_METHOD'] === 'OPTIONS') {
        header('Access-Control-Allow-Origin: *');
        header('Access-Control-Allow-Methods: POST, GET, DELETE, PUT, PATCH, OPTIONS');
        header('Access-Control-Allow-Headers: token, Content-Type');
        header('Access-Control-Max-Age: 1728000');
        header('Content-Length: 0');
        header('Content-Type: text/plain');
        die();
    }

    header('Access-Control-Allow-Origin: *');
    header('Content-Type: application/json');

    $ret = [
        'result' => 'OK',
    ];
    print json_encode($ret);

I've simply managed to get dropzone and other plugin to work with this fix (angularjs + php backend)

 header('Access-Control-Allow-Origin: *'); 
    header("Access-Control-Allow-Credentials: true");
    header('Access-Control-Allow-Methods: GET, PUT, POST, DELETE, OPTIONS');
    header('Access-Control-Max-Age: 1000');
    header('Access-Control-Allow-Headers: Origin, Content-Type, X-Auth-Token , Authorization');

add this in your upload.php or where you would send your request (for example if you have upload.html and you need to attach the files to upload.php, then copy and paste these 4 lines). Also if you're using CORS plugins/addons in chrome/mozilla be sure to toggle them more than one time,in order for CORS to be enabled

If you want to create a CORS service from PHP, you can use this code as the first step in your file that handles the requests:

// Allow from any origin
if(isset($_SERVER["HTTP_ORIGIN"]))
{
    // You can decide if the origin in $_SERVER['HTTP_ORIGIN'] is something you want to allow, or as we do here, just allow all
    header("Access-Control-Allow-Origin: {$_SERVER['HTTP_ORIGIN']}");
}
else
{
    //No HTTP_ORIGIN set, so we allow any. You can disallow if needed here
    header("Access-Control-Allow-Origin: *");
}

header("Access-Control-Allow-Credentials: true");
header("Access-Control-Max-Age: 600");    // cache for 10 minutes

if($_SERVER["REQUEST_METHOD"] == "OPTIONS")
{
    if (isset($_SERVER["HTTP_ACCESS_CONTROL_REQUEST_METHOD"]))
        header("Access-Control-Allow-Methods: POST, GET, OPTIONS, DELETE, PUT"); //Make sure you remove those you do not want to support

    if (isset($_SERVER["HTTP_ACCESS_CONTROL_REQUEST_HEADERS"]))
        header("Access-Control-Allow-Headers: {$_SERVER['HTTP_ACCESS_CONTROL_REQUEST_HEADERS']}");

    //Just exit with 200 OK with the above headers for OPTIONS method
    exit(0);
}
//From here, handle the request as it is ok

CORS can become a headache, if we do not correctly understand its functioning. I use them in PHP and they work without problems. reference here

header("Access-Control-Allow-Origin: *");
header("Access-Control-Allow-Credentials: true");
header("Access-Control-Max-Age: 1000");
header("Access-Control-Allow-Headers: X-Requested-With, Content-Type, Origin, Cache-Control, Pragma, Authorization, Accept, Accept-Encoding");
header("Access-Control-Allow-Methods: PUT, POST, GET, OPTIONS, DELETE");

This much code works down for me when using angular 4 as the client side and PHP as the server side.

header("Access-Control-Allow-Origin: *");

this should work

header("Access-Control-Allow-Origin: *");
header("Access-Control-Allow-Headers: X-Requested-With, Content-Type, Origin, Cache-Control, Pragma, Authorization, Accept, Accept-Encoding");

add this code in .htaccess

add custom authentication key's in header like app_key,auth_key..etc

Header set Access-Control-Allow-Origin "*"
Header set Access-Control-Allow-Headers: "customKey1,customKey2, headers, Origin, X-Requested-With, Content-Type, Accept, Authorization"

I used these 5 headers and after that solved the cors error(backend: PHP, Frontend: VUE JS)

header('Access-Control-Allow-Origin: *');
header('Access-Control-Allow-Methods: GET, PUT, POST, DELETE, OPTIONS, post, get');
header("Access-Control-Max-Age", "3600");
header('Access-Control-Allow-Headers: Origin, Content-Type, X-Auth-Token');
header("Access-Control-Allow-Credentials", "true");