In all seriousness, PHP allows one to switch between scripting and outputting HTML in the same file. Example:
<?php
$title = "testing";
?>
<html>
<head>
<title><?php echo $title; ?></title>
</head>
<body>
Wow, look, I'm normal text in an HTML document!
</body>
</html>
The colored bits are PHP. The rest is HTML. This file would be saved as something.php, but that doesn't change the fact that the black-and-white bits are HTML.