PHP：由于传递了param类型而导致请求错误

Question

So, my php is terrible being an FE engineer but need to fix something fairly quick.

I'm hitting an endpoint of an API that stack trace errors to/on this BE function:

/**
* 
* @param string $token
* @return \stdClass|null
*/
protected function getInstance(string $token)
 {
     $instance = PubSub::getInstance($token);
     return $instance;
 }

Here is my fe code that is hitting it (angular1):

$http({
    method: 'PUT',
    url: $rootScope.quizURI + '/API/quiz/control/timer',
    headers: {
        'Content-Type': 'application/json',
        'Authorization': $rootScope.teacher_token
    },
    data: {
        'instance_token': $rootScope.teacherInstanceToken
    }
    }).then(function successCallback(response) {
        $log.debug('response from control timer put', response);
    });

Workings:

• Yes, $rootScope.teacher_token is a string.
• Yes, here there's a response error in the browser console:

Fatal error: Uncaught TypeError: Argument 1 passed to API\Controller\Base::getInstance() must be of the type string, null given, called

Any pointers would make my Easter ;)

EDIT:

Blunder on my part. A var was undefined wa wa waaaaa