<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<?php
session_start();
$_SESSION['test4']='Hello from index!';
var_dump($_SESSION['test4']);
var_dump($_SESSION['test3']);
echo $_SESSION['test4'];
?>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Title</title>
<link href="css/style.css" rel="stylesheet" type="text/css" />
<link href="https://fonts.googleapis.com/css?family=Roboto:400,700&subset=cyrillic" rel="stylesheet">
</head>
<body>
</body>
</html><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<?php
session_start();
var_dump($_SESSION['test4']);
var_dump($_SESSION['test1']);
$_SESSION['test2']='Это сообщение из test1';
$_SESSION['test3']='Это сообщение из test1';
?>
<html>
<head>
<link rel="stylesheet" type="text/css" href="sss/style.css">
</head>
<body>
<a href="index.php">Ссылка</a>
</body>
</html>