AngularJS（前端）和Laravel（后端）中的JSON / Arrays中为NULL

I am having difficulty how I can handle null values. Whenever I send JSON to server, all null values in front-end becomes "null" as string. How should I handle this?

AngularJS: In my controller. I am sending values from a form using ng-file-upload plugin https://github.com/danialfarid/ng-file-upload/wiki/PHP-Example

$scope.saveNewDocument = function(){
    var formAttachments = Upload.upload({
        url: appServer.baseURL + appServer.api.generalDocuments, 
        method: 'POST',
        file: $scope.formData.formAttachments,
        sendFieldsAs: 'form',
        fields: $scope.formData // $scope.formData is ng-model in view forms
    }).then(function(success){
        //some codes
    }, function(error){
        console.log(error);
    });
};

Laravel: In my controller.

 public function store(Request $request)
    {

        $request = $request->all();

        //if I get values from request. All null becomes "null"

    }

Since you haven't provided with any code, I'm not sure exactly about your problem but assuming to solve this problem in PHP (which this is tagged as) you can write a simple if statement and check the data before sending as follows:

if($var==null)
    $var=0;