Facebook Chat bot (PHP webhook) sending multiple replies

Question

My Facebook chat bot is working but it's sending back multiple messages after my initial message to it. This is my webhook script (i appreciate it's a very rough working example):

$challenge = $_REQUEST['hub_challenge'];
$verify_token = $_REQUEST['hub_verify_token'];

if ($verify_token === 'MY_VERIFICATION_TOKEN') {
  echo $challenge;
}

$input = json_decode(file_get_contents('php://input'), true);

$sender = $input['entry'][0]['messaging'][0]['sender']['id'];
$message = $input['entry'][0]['messaging'][0]['message']['text'];


//API Url
$url = 'https://graph.facebook.com/v2.6/me/messages?access_token=<my-token>';

//Initiate cURL.
$ch = curl_init($url);

//The JSON data.
$jsonData = '{
    "recipient":{
        "id":"'.$sender.'"
    }, 
    "message":{
        "text":"Hey Lee!"
    }
}';

//Encode the array into JSON.
$jsonDataEncoded = $jsonData;

//Tell cURL that we want to send a POST request.
curl_setopt($ch, CURLOPT_POST, 1);

//Attach our encoded JSON string to the POST fields.
curl_setopt($ch, CURLOPT_POSTFIELDS, $jsonDataEncoded);

//Set the content type to application/json
curl_setopt($ch, CURLOPT_HTTPHEADER, array('Content-Type: application/json'));

//Execute the request
$result = curl_exec($ch);

Answer 1

FB hits your webhook url with the original incoming message and you process it. You are then sending a response back to the user and the script ends. Then, once the message is delivered to the user, FB sends a delivery confirmation to the webhook url. Since your script is always set to send "Hey Lee!" any time that it is called, the delivery callback is actually triggering another message to be sent, and then another delivery confirmation comes in, and then that process is repeating it self. To fix this, put an if statement around your code to send a message. Here's an example.

$challenge = $_REQUEST['hub_challenge'];
$verify_token = $_REQUEST['hub_verify_token'];

if ($verify_token === 'MY_VERIFICATION_TOKEN') {
  echo $challenge;
}

$input = json_decode(file_get_contents('php://input'), true);

$sender = $input['entry'][0]['messaging'][0]['sender']['id'];
$message = $input['entry'][0]['messaging'][0]['message']['text'];


//API Url
$url = 'https://graph.facebook.com/v2.6/me/messages?access_token=<my-token>';

//Initiate cURL.
$ch = curl_init($url);

if($message=="hello")
{
        //The JSON data.
        $jsonData = '{
        "recipient":{
                "id":"'.$sender.'"
        },
        "message":{
                "text":"Hey Lee!"
        }
        }';
}

//Encode the array into JSON.
$jsonDataEncoded = $jsonData;

//Tell cURL that we want to send a POST request.
curl_setopt($ch, CURLOPT_POST, 1);

//Attach our encoded JSON string to the POST fields.
curl_setopt($ch, CURLOPT_POSTFIELDS, $jsonDataEncoded);

//Set the content type to application/json
curl_setopt($ch, CURLOPT_HTTPHEADER, array('Content-Type: application/json'));

//Execute the request
$result = curl_exec($ch);

Hope that helps.