[ 'id' => $senderId ],
'message' => [ 'text' => $answer ]
];
$ch = curl_init('https://graph.facebook.com/v2.6/me/messages?access_token='.$accessToken);
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode($response));
curl_setopt($ch, CURLOPT_HTTPHEADER, ['Content-Type: application/json']);
curl_exec($ch);
curl_close($ch);
