[REQ] [PHP] Allow user to return binary data of file directly instead of temp file

Is your feature request related to a problem? Please describe.

Not related to a problem, merely an enhancement

Describe the solution you'd like

Currently when an endpoint return type is defined in the OAS as the following:

       "responses": {
          "200": {
            "description": "successful operation",
            "headers": {},
            "content": {
              "application/octet-stream": {
                "schema": {
                  "type": "string",
                  "description": "successful operation",
                  "format": "binary"
                }
              }
            }
          },

the client generates a method that returns a reference to an SplFileObject

Ex:

$config = \OpenAPI\Client\Configuration::getDefaultConfiguration()
->setUsername(getenv('API_USERNAME'))
->setPassword(getenv('API_PASSWORD'));

$apiInstance = new \OpenAPI\Client\Api\MediaApi(
    new \GuzzleHttp\Client(),
    $config
);

$account_id = getenv('ACCOUNT_ID'); // string

try {
    $result = $apiInstance->getMedia($account_id, 'test.png');
    print_r($result);
} catch (Exception $e) {
    echo 'Exception when calling MediaApi->getMedia: ', $e->getMessage(), PHP_EOL;

Output:

SplFileObject Object
(
    [pathName:SplFileInfo:private] => /private/var/folders/89/vf520s8j5xx5m6qp344kcb_r0000gp/T/THzOgp
    [fileName:SplFileInfo:private] => THzOgp
    [openMode:SplFileObject:private] => r
    [delimiter:SplFileObject:private] => ,
    [enclosure:SplFileObject:private] => "
)

And then to write that to a file the user must use the fread() method of the SplFileObject Object

$myfile = fopen("testfile.png", "w");
fwrite($myfile, $result->fread($result->getSize()));
fclose($myfile);

It would be cleaner to be able to pass the binary string directly to the user with a binary=True flag in the getMedia method that the user could then write directly to a file and not have to worry about a temp file.

Describe alternatives you've considered

No alternatives available - the client SDK basically forces this method for anything that is a binary file

This if in the {}Api file ensures the stream goes to the serializer and a temp file is generated

            switch($statusCode) {
                case 200:
                    if ('\SplFileObject' === '\SplFileObject') {
                        $content = $response->getBody(); //stream goes to serializer
                    } else {
                        $content = (string) $response->getBody();
                    }

Start by tracing the generated PHP {}Api response switch for status 200, especially the SplFileObject branch shown in the issue, and identify the generator source that produces it. Define how a binary option should select a direct string while preserving the existing temporary-file behavior, then verify the generated client returns the requested representation for an application/octet-stream binary response.