<link href="//maxcdn.bootstrapcdn.com/bootstrap/4.1.1/css/bootstrap.min.css" rel="stylesheet" id="bootstrap-css">
<script src="//maxcdn.bootstrapcdn.com/bootstrap/4.1.1/js/bootstrap.min.js"></script>
<script src="//cdnjs.cloudflare.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
<!------ Include the above in your HEAD tag ---------->
<?php
session_start();
if(!isset($_SESSION['id_usuario']))
{
header("location: telalogin.php");
exit;
}
?>
SEJA BEEEEEEEM VINDOOOOO!!
<a href="sair.php"> Sair </a>