<?php
// (A) START SESSION 
session_start();

// (B) HANDLE LOGIN
if (isset($_POST['user']) && !isset($_SESSION['user'])) {
  // (B1) USERS & PASSWORDS - SET YOUR OWN !
  $users = [
    "joe" => "123456",
    "jon" => "654321",
    "joy" => "987654"
  ];

  // (B2) CHECK & VERIFY
  if (isset($users[$_POST['user']])) {
    if ($users[$_POST['user']] == $_POST['password']) {
      $_SESSION['user'] = $_POST['user'];
    }
  }

  // (B3) FAILED LOGIN FLAG
  if (!isset($_SESSION['user'])) { $failed = true; }
}

// (C) REDIRECT USER TO HOME PAGE IF SIGNED IN
if (isset($_SESSION['user'])) {
  header("Location: index.htm"); // SET YOUR OWN HOME PAGE!
  exit();
}