Well. I provided the wrong parameter there. So that function didn't work. Its a working function.

you have to take these,

accesstoken = your access token

other params -

    $raw_input = file_get_contents('php://input');
    if(!empty($raw_input)){
        $input = json_decode($raw_input, true); 
        $messageId = $input['entry'][0]['changes'][0]['value']['messages'][0]['id'];
         $phoneId = $input['entry'][0]['changes'][0]['value']['metadata']['phone_number_id'];