<?php

session_start();

// Usuários cadastrados
$user = "admin";
$pass = "admin";

/* Sair */
if (isset($_GET['logout'])) {
	unset($_SESSION['login']);
}

/* Caso o usuário esteja logado */
if (isset($_SESSION['login']) && $_SESSION['login'] == $pass) {
	login_sucesso($user);
}

/* Formulário de login preenchido */
else if (isset($_POST['submit'])) {
	if ($_POST['username'] == $user && $_POST['password'] == $pass) {
		//IF USERNAME AND PASSWORD ARE CORRECT SET THE LOGIN SESSION
		$_SESSION["login"] = $pass;
		header("Location: $_SERVER[PHP_SELF]");
	} else {
		// DISPLAY FORM WITH ERROR
		login_formulario();
		login_erro();
	}
}

/* Mostra o formulário de login */
else {
	login_formulario();
}

/* Templates */
function login_formulario() {
	echo '<form action="' . isset($self) . '" method="post" autocomplete="off">' .
			'<input type="text" name="username" placeholder="Nome de usuário...">' .
			'<input type="password" name="password" placeholder="Senha...">' .
			'<input type="submit" name="submit" value="Login">' .
		'</form>';
}

function login_sucesso($username) {
	echo '<p>Hello ' . $username . ', you have successfully logged in!</p>' .
		'<a href="?logout=true">Logout</a>';
}

function login_erro() {
	echo '<p>Username or password is invalid</p>';
}

?>