PHP
(a quick example)
HTML LOGIN FORM <form method="post"> <input type="text" name="user"> <input type="password" name="pass"> <input type="submit" value="Log In"> </form>
PROCESS LOGIN ON FORM SUBMIT <?php require "LOGIN.PHP"; ?>
START SESSION session_start();
if (isset($_POST["user"]) && !isset($_SESSION["user"])) { USERS LIST $usr = ["joe" => "123456"]; CHECK & VERIFY if (isset($usr[$_POST["user"]]) && $usr[$_POST["user"]]==$_POST["pass"]) { $_SESSION["user"] = $_POST["user"]; } }
REDIRECT TO HOME PAGE ON LOGIN if (isset($_SESSION["user"])) { header("Location: index.php"); exit(); }
ON TOP OF ALL PAGES - CHECK IF USER SIGNED IN if (!isset($_SESSION["user"])) { header("Location: login.php"); exit(); }
LOGOUT FORM <form method="post"> <input type="hidden" name="logout" value="1"> <input type="submit" value="Logout"> </form>
PHP END SESSION if (isset($_POST["logout"])) { unset($_SESSION); session_destroy(); }