<?
setcookie('greeting', 'yes');
?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<head>
<title>Mimsy Were the Borogoves</title>
<meta http-equiv="Content-Type" content="text/html;charset=utf-8" />
<meta name="description" content="Hello, World." />
</head>
<body>
<h1>World</h1>
<?IF ($_COOKIE['greeting'] == 'yes'):?>
<p>World, say hello.</p>
<?ELSE:?>
<p>Please go away.</p>
<?ENDIF;?>
</body>
</html>
What will this page display? The answer has to do with HTTP headers and the way that browsers and servers communicate with each other.