谷歌云 PHP CORS 问题

Question

I have migrated a PHP api to google cloud functions using the PHP (beta) language. The code requests data from an external application which is returned in an XML format and then the API gets the results and outputs them as JSON for the angular app to read

My code works when using POSTMAN (so I know it returns the correct data) but when running from my Angular app either locally or hosted on google firebase I get the below CORS issue

Request URL: [[google firebase cloud function url]]
Request Method: OPTIONS
Status Code: 500
Referrer Policy: strict-origin-when-cross-origin

Provisional headers are shown
Accept: application/json, text/plain, */*
Content-Type: application/moca-xml
Referrer: http://localhost:4200/
Response-Encoder: application/xml
Response-Type: text

Request Payload:
[[Data sent to external app to request data ]]

The original PHP API used got around CORS by setting headers:

//set header of return output
header('Access-Control-Allow-Origin: *'); 
header("Access-Control-Allow-Credentials: true");
header('Access-Control-Allow-Methods: POST');
header('Access-Control-Max-Age: 1000');
header('Access-Control-Allow-Headers: Origin, Content-Type, Response-Encoder, Response-Type');  
header('Content-Type: application/json');

In the google firebase cloud function, both using the above or the suggested below method have no effect and result in the CORS errors

$headers = ['Access-Control-Allow-Origin' => '*'];
$headers = array_merge($headers, [
            'Access-Control-Allow-Methods' => 'POST, OPTIONS',
            'Access-Control-Allow-Credentials' => 'true',
            'Access-Control-Allow-Headers' => 'Origin, Content-Type, Response-Encoder, Response-Type',
            'Access-Control-Max-Age' => '1000',
            'Content-Type' => 'application/json'            
        ]);

.... code to get data ....

return new Response(200, $headers, $returndata);

Answer 1

Firstly the angular app calling the google cloud PHP function was not allowed certain headers and in the end my header was just

private headers = new HttpHeaders({'Content-Type':'application/json'});

Then in the google cloud PHP function, the OPTIONS request has to be handled by returning 200 or 204 as well as setting the headers on the response

 $headers = ['Access-Control-Allow-Origin' => '*'];
 if ($request->getMethod() === 'OPTIONS') {
     $headers = array_merge($headers, [
            'Access-Control-Allow-Methods' => 'GET',
            'Access-Control-Allow-Headers' => 'Content-Type',
            'Access-Control-Max-Age' => '3600'          
        ]);
    return new Response(200, $headers, '');
 } else {
     $headers = array_merge($headers, [
                'Access-Control-Allow-Methods' => 'POST',
                'Access-Control-Allow-Credentials' => 'true',
                'Access-Control-Allow-Headers' => 'Origin, Content-Type',
                'Access-Control-Max-Age' => '1000', 
                'Content-Type' => 'application/json'    
            ]);
 }