user registration via telegram

.gitignore

@@ -0,0 +1,2 @@
+settings.ini
+.vscode/*

webhook/index.php

@@ -0,0 +1,78 @@
+<?php
+$config = parse_ini_file("../settings.ini");
+$dbh = new PDO('mysql:host=localhost;dbname=test', 'root');
+
+$request = file_get_contents( 'php://input' );
+$request = json_decode( $request, TRUE );
+
+function send($id, $msg, $config) {
+    $url = $config['telegram_api'].'bot'.$config['telegram_key'].'/sendMessage';
+    $data = array(
+        'chat_id' => $id, 
+        'text' => $msg
+    );
+    $options = array(
+        'http' => array(
+            'header'  => "Content-type: application/x-www-form-urlencoded\r\n",
+            'method'  => 'POST',
+            'content' => http_build_query($data)
+        )
+    );
+    $context  = stream_context_create($options);
+    $result = file_get_contents($url, false, $context);
+    if ($result === FALSE) { return FALSE; }
+    return TRUE;
+}
+
+if( !$request )
+{
+    die();
+}
+elseif( !isset($request['update_id']) || !isset($request['message']) )
+{
+    die();
+}
+else
+{
+    $chatId  = $request['message']['chat']['id'];
+    $message = $request['message']['text'];
+    $user_id = $request['message']['from']['id'];
+    $username = $request['message']['from']['username'];
+    
+    if($message == '/start')
+    {
+        $stmt = $dbh->query(
+            'SELECT id FROM `contact`
+            WHERE user_id = "'.$user_id.'"'
+        );
+        if($stmt->rowCount() == 0)
+        {
+            $stmt = $dbh->query(
+                'INSERT into contact (username, user_id) 
+                VALUES ("'.$username.'","'.$user_id.'")'
+                );
+            send(
+                $user_id, 
+                'Hello! Send me an URL and i will notify you when topic will be updated.', 
+                $config
+            );
+        }
+        else
+        {
+            send(
+                $user_id, 
+                'Hello again. Send me an URL and i will notify you when topic will be updated.', 
+                $config
+            );
+            die();
+        }
+    // if message is an URL
+    }elseif(!(filter_var($message, FILTER_VALIDATE_URL) === FALSE)) {
+        send(
+            $user_id, 
+            'Recognized as an URL', 
+            $config
+        );
+    }
+}
+?>