added login, logout and registration sites and functionality as well as an protected profile page

controllers/login.php

@@ -1,3 +1,28 @@
 <?php
-    $heading = "Login";
-    require "views/login.view.php";
+$heading = "Login";
+$username = "MatheApp";
+$password = "password";
+$config = require('config.php');
+$db = new Database($config['database'], $username, $password);
+
+if (isset($_POST["submit"])) {
+  $stmt = $db->query("SELECT * FROM user WHERE username = :user", ['user' => $_POST["username"]])->get();
+  $count = sizeof($stmt);
+  if ($count == 1) {
+    $stmt = $stmt[0];;
+    
+    if (password_verify($_POST['password'], $stmt["password"])) {
+      session_start();
+      $_SESSION["username"] = $stmt['username'];
+      //require "views/profile.php";
+      //urlIs("/profile");
+      header("Location: /profile");
+    } else {
+      echo "Anmeldung fehlgeschlagen!";
+    }
+  } else {
+    echo "Anmeldung fehlgeschlagen!";
+  }
+}
+
+   require "views/login.view.php";