fakebook.com 1.1

<?php
//GLOBAL
$RUNNING = true;
global $USER_IN_SESSION;
$USER_IN_SESSION = false;
function art(){
    echo "
 _____   ____    __    ___  ____    ___    ___   _
|     | /    |  /  ]  /  _]|    \  /   \  /   \ | |
|   __||  o  | /  /  /  [_ |  o  )|     ||     || |
|  |_  |     |/  /  |    _]|     ||  O  ||  O  || |___
|   _] |  _  /   \_ |   [_ |  O  ||     ||     ||     |
|  |   |  |  \     ||     ||     ||     ||     ||     |
|__|   |__|__|\____||_____||_____| \___/  \___/ |_____| stable 1.1
Commands:

/login      /logout     /checkloginstatus       /exit\n\n
";
}
art();
$users = array("user1" => "1234", "user2" => "5678", "user3" => "abcd", "user4" => "efgh",
                "user5" => "ijkl", "user6" => "mnop", "user7" => "qrst", "user8" => "uvwx");
function login($username, $password, $users){
    global $USER_IN_SESSION;
    if (array_key_exists($username, $users)) {
        $stored_password = $users[$username];
        if ($password == $stored_password) {
            echo "Login successful.\n";
            $USER_IN_SESSION = true;
        }
        else {
            echo "Incorrect password.\n";
        }
        //echo "Username exists in \$users.\n";
    } else {
        echo "Username does not exist in \$users.\n";
    }
}
function logout($username) {
    global $USER_IN_SESSION;
        if ($USER_IN_SESSION == true) {
            echo "{$username} logged out.\n";
            $username = NULL;
            $password = NULL;

            $USER_IN_SESSION = false;
        }
        else {
            echo "Already logged out!\n";
        }
}
function isLoggedIn($username){
    global $USER_IN_SESSION;
    if ($USER_IN_SESSION == true) {
        echo "{$username} is currently logged in.\n";
    }
    else {
        echo "No one is currently logged in.\n";
    }
}
while($RUNNING == true) {
  global $USER_IN_SESSION;
  if ($USER_IN_SESSION != true) {
     $user_input = readline();
  }
  else {
      fwrite(STDOUT, "{$username}> ");
        $user_input = readline();
  }

  //user actions
  switch ($user_input) {
    case "/exit":
        $RUNNING = false;
        break;
    case "/login":
        global $USER_IN_SESSION;
        if ($USER_IN_SESSION == false) {
            echo "Enter Username: ";
            $username = readline();
            echo "Enter Password: ";
            $password = readline();

            login($username, $password, $users);
        }
        elseif ($USER_IN_SESSION == true) {
            echo "Already logged in as '{$username}'.\n";
        }
        break;
    case "/logout":
        logout($username);
        break;
    case "/checkloginstatus":
        global $USER_IN_SESSION;
        if ($USER_IN_SESSION == true) {
            isLoggedIn($username);
        }
        else {
            echo "No user is currently logged in.\n";
        }
        break;
    case "/help":
        echo "___________________________________________________\n\n/login\t\t\tLogin\n/logout\t\t\tTo logout\n/checkloginstatus\tTo check login status\n/exit\t\t\tTo exit\n___________________________________________________\n\n";
        break;
    //debug
    case "inf":
        echo "\ncurrent user: {$username}\n";
        echo "user password: {$password}\n";
        echo $USER_IN_SESSION ? '$USER_IN_SESSION: true' : '$USER_IN_SESSION: false';
        echo "\n";
        break;
    default:
        echo "'{$user_input}' is not recognized as an internal or external command, For more information on a specific command, type /help.\n";
  }
}
?>