如何正确解析API响应

My Problem is relatively simple:

I make an API call and get the following answer in response:

[{"RowKey":24764}] 

The Content-Type I'm receiving is text/html

Somehow, I'm just not able to parse this correctly. neither json_encodeor json_decodeseems to help.

I'm trying to Map the object into my response class:

class ApiResponse {

  public $schedules = [];

}

with the json object mapper from: https://github.com/mintware-de/json-object-mapper

Consider this test case:

$response = '[{"RowKey":24764}]';
$result = json_decode($response, true);
echo $result[0]['RowKey']; // Output: 24764