Unable to pass Authorization header from URLRequest in iOS

I'm having problems accessing the Authorization header when sending a GET request from URLRequest in Swift.

I've made a simple script that converts the $_SERVER parameter to JSON and outputs to the browser to test that I'm sending the Authorization header correctly.

Here's my PHP code:

echo json_encode($_SERVER);
exit;

Here's my .htaccess file

RewriteEngine On
RewriteBase /
SetEnvIf Authorization "(.*)" HTTP_AUTHORIZATION=$1
RewriteCond %{HTTP:Authorization} ^(.+)$
RewriteRule .* - [E=HTTP_AUTHORIZATION:%{HTTP:Authorization}]

When I send a request via PHP or using the Postman application, I get the following response:

 { "TZ": "Etc/UTC", "REDIRECT_REDIRECT_UNIQUE_ID": "WQOWeWALzYlxj8TEssOrHgAAACA", "REDIRECT_REDIRECT_SCRIPT_URL": "/", "REDIRECT_REDIRECT_SCRIPT_URI": "/", "REDIRECT_REDIRECT_HTTP_AUTHORIZATION": "12345678", "REDIRECT_REDIRECT_HTTPS": "on", "REDIRECT_REDIRECT_SSL_TLS_SNI": "/", "REDIRECT_REDIRECT_STATUS": "200", "REDIRECT_UNIQUE_ID": "WQOWeWALzYlxj8TEssOrHgAAACA", "REDIRECT_SCRIPT_URL": "/", "REDIRECT_SCRIPT_URI": "/", "REDIRECT_HTTP_AUTHORIZATION": "12345678", ....etc....

The REDIRECT_REDIRECT_HTTP_AUTHORIZATION and REDIRECT_HTTP_AUTHORIZATION parameters return the value passed in the Authorisation header as expected.

When I try the same request using URLRequest in Swift the REDIRECT_REDIRECT_HTTP_AUTHORIZATION parameter is empty.

Here's my Swift code:

var url = URL(string: urlString)!
var request : URLRequest!
request.httpMethod = "GET"
request.setValue(auth, forHTTPHeaderField: "Authorization")
request.setValue("test", forHTTPHeaderField: "Hello")
URLSession.shared.dataTask(with: request as URLRequest, completionHandler: { (data, response, error) -> Void in
do { guard let responseData = data else {return} guard let jsonData = try JSONSerialization.jsonObject(with: responseData, options: []) as? NSDictionary else {return} print(jsonData)

I get the following response:

{ . . . "HTTP_HELLO" = test; "REDIRECT_HANDLER" = "application/x-httpd-ea-php56"; "REDIRECT_HTTPS" = on; "REDIRECT_REDIRECT_HTTPS" = on; "REDIRECT_REDIRECT_HTTP_AUTHORIZATION" = ""; "REDIRECT_REDIRECT_SCRIPT_URI" = "/"; "REDIRECT_REDIRECT_SCRIPT_URL" = "/"; "REDIRECT_REDIRECT_STATUS" = 200; "REDIRECT_URL" = "/api/index.php"; "REMOTE_ADDR" = "149.12.15.210"; "REMOTE_PORT" = 64235; "REQUEST_METHOD" = GET; "REQUEST_SCHEME" = https; "REQUEST_TIME" = 1493407944; . . . }

The REDIRECT_REDIRECT_HTTP_AUTHORIZATION parameter is empty.

I can see that the HTTP_HELLO header is set to "test" so the problem doesn't seem to be in the Swift code.

This issue only seems to affect requests sent using URLRequest in Swift.

I assume the problem is on the server side and possibly in the .htaccess file but I can't find a way to get this working correctly.

The server runs CentOS 7 WHM/cpanel. I'm able to make changes to the WHM/cpanel settings if required.

Any help would be appreciated as I can't see what could cause the REDIRECT_REDIRECT_HTTP_AUTHORIZATION to be empty.

Thanks.