Copy this code and paste it in your HTML
<?php
if($_GET['acao']=="logar"){
$senha = $_POST['pwd'];
if($senha=="trielo"){
$_SESSION['userName'] = "UserNameXXX";
$_SESSION['HTTP_USER_AGENT'] = md5($_SERVER['HTTP_USER_AGENT']); header("Location: /home.php"); } else {
echo "Senha incorreta!";
}
}
?>
//other pages
<?php
if((!$_SESSION['userName'])||($_SESSION['HTTP_USER_AGENT'] != md5($_SERVER['HTTP_USER_AGENT']))){ }
?>