src/CurlService.php
public function requestJson($method, $url, $options=array()){
        $options['headers'][] = 'Content-Type: application/json';
        $options['headers'][] = 'Content-Length: ' . strlen($options['body']);
        $this->request($method, $url, $options);
    }
public function requestJson($method, $url, $options=array()){
        $options['headers'][] = 'Content-Type: application/json';
        $options['headers'][] = 'Content-Length: ' . strlen($options['body']);
        $this->request($method, $url, $options);
    }
request as body data is json
if you want to request Json, set Content-Type and Length;