Mailgun webhook for delivering messages to Telegram Channel

mg-webhook.php

<?php

// check for POST method
if ($_SERVER['REQUEST_METHOD'] == 'POST') {
        // get payload data
        $post = json_decode(file_get_contents('php://input'), true);
        $signature = $post['signature'];
        $data = $post['event-data'];
        $key = "MAILGUNAPIKEY";

        // verify legitimacy of payload
        if (hash_hmac('sha256', $signature['timestamp'] . $signature['token'], $key) === $signature['signature']) {

                // detect type of message
                if ($data['event'] == "delivered") {
                        // successful delivery
                        $message = "👍 SUCCESS delivery to " . $data['message']['headers']['to'] . " with subject " . $data['message']['headers']['subject'];
                        
                } elseif ($data['event'] == "failed" && $data['severity'] == "temporary") {
                        // temporary failure (unknown address)
                        $message = "🚨 UNRECOGNIZED ADDRESS FAILED delivery to " . $data['message']['headers']['to'] . " with subject " . $data['message']['headers']['subject'];

                } elseif ($data['event'] == "failed" && $data['severity'] == "permanent") {
                        // permanent failure
                        $message = "🚨 FAILED delivery to " . $data['message']['headers']['to'] . " with subject " . $data['message']['headers']['subject'];
                        
                } elseif ($data['event'] == "complained") {
                        // spam complaint recieved
                        $message = "🚨 SPAM reported from delivery to " . $data['message']['headers']['to'] . " with subject " . $data['message']['headers']['subject'];
                        
                } elseif ($data['event'] == "unsubscribed") {
                        // unsubscribed
                        $message = "🚫 " . $data['recipient'] . " unsubscribed from " . $data['geolocation']['city'] . ", " . $data['geolocation']['region'] . " (" . $data['geolocation']['country'] . ")";
                        
                } elseif ($data['event'] == "clicked") {
                        // clicked
                        $message = "✅ " . $data['recipient'] . " clicked from " . $data['geolocation']['city'] . ", " . $data['geolocation']['region'] . " (" . $data['geolocation']['country'] . ")";
                        
                } elseif ($data['event'] == "opened") {
                        // opened the message
                        $message = "✅ " . $data['recipient'] . " opened from " . $data['geolocation']['city'] . ", " . $data['geolocation']['region'] . " (" . $data['geolocation']['country'] . ")";
                        
                } else {
                        $message = "Unrecognized event.";
                }

                // send notice to telegram
                $ch = curl_init();
                curl_setopt($ch, CURLOPT_URL, "https://api.telegram.org/BOTIDHERE/sendMessage");
                curl_setopt($ch, CURLOPT_POST, 1);
                curl_setopt($ch, CURLOPT_POSTFIELDS, "chat_id=CHATIDHERE&text=$message");
                curl_exec($ch);
                curl_close($ch);
                echo $message;
        } else {
                echo "Unable to verify payload.";
        }
}


?>

MAILGUNAPIKEY = Mailgun webhook signing key