无法使用twilio代理录制呼叫

I have setup twilio proxy for communication between two people. I want to record a call from both sides. I have set interceptCallbackUrl of proxy service. I am not able to record calls. Below is my code.

if($_POST['inboundResourceType'] == 'call'){            
   $recording = $twilio->calls($_POST['inboundResourceSid'])
                    ->recordings
                    ->create();
}