How to post json data to a php script with $http.post

I've been having this problem for a while and tried many solutions which haven't worked. I am trying to use $http.post to send json data to a php script named processCustomers.php which is part of my API

The post request is

angular.extend(obj, {id: id});
  $http({
    method: 'POST',
    url: '../API/processCustomers.php',
    headers: { 'Content-Type': 'application/json' },
    dataType: 'json',
    data: obj
   }).success(function (data) {
    console.log(data);
  });
};

and the processCustomers is

$newCustomers = filter_has_var(INPUT_POST, 'newCustomer');
if ($newCustomers) {#request to add new customer

    $exceptionalFields = ['customerID']; //

    $customersJSON = json_decode(filter_input(INPUT_POST, "newCustomer"));



    if (json_last_error() > 0) {
        echo DotCom::systemFeedBack("Sorry customer not created unknown error", "data sent is not a json object", 303);
        return;
    }



    foreach ($customersJSON as $key => $customer) {
        $parameterTypes = ""; # order determined by the sql returned by validateInputData()


    $entries = $func->validateInputData($tableMetaData,$customer, $parameterTypes, $exceptionalFields);


    if (!is_array($entries)) {
        echo $entries;
        return;
    }

     $results = $customers->createCustomer($entries, $parameterTypes, $link,$status);

When I send the request, the console in the browser says the response is text/html instead of application/json.I looked through many tutorials and examples and I also have tried the folowings: removing the headers and datatype - no effect wrapping the obj in JSON.stringify - results in header changing to application/x-www-form-urlencoded