<?php session_start();

//connection to database and other stuff

if ($user == $dbuser && $pass == $dbpass) {

    $_SESSION['user'] = $user;
    $_SESSION['authenticated'] = "yes";
    $suser = $_SESSION['user']; //just to test if session works

}

?>

<?php session_start(); ?>

//small amount of html here

<?php
    $suser = $_SESSION['user'];
    $sauth = $_SESSION['authenticated'];

    if ($sauth != 'yes') { //not completed yet (needs user name check)
        echo "<a href='./'>Log in</a> first!";
        require ('./login.php');
        die;
    } else {
    //not so important code here
    }
?>

//rest of html here

<?php session_start();
ob_start();
//connection to database and other stuff

if ($user == $dbuser && $pass == $dbpass) {

    $_SESSION['user'] = $user;
    $_SESSION['authenticated'] = "yes";
    $suser = $_SESSION['user']; //just to test if session works

}

?>

<?php session_start();
  ob_start();?>

//small amount of html here
<?php session_start(); ob_start();
    $suser = $_SESSION['user'];
    $sauth = $_SESSION['authenticated'];

    if ($sauth != 'yes') { //not completed yet (needs user name check)
        echo "<a href='./'>Log in</a> first!";
        require ('./login.php');
        die;
    } else {
    //not so important code here
    }
?>

//rest of html here