Far too simple for me to understand, I guess!
The most basic php in html I can think of:
<html>
<head>
<h3>PHP Testing</h3>
</head>
<body>
<?php echo '<p>Something or anything!</p>'; ?>
</body>
</html>
Everything is rendered correctly by the browser (Firefox) up to and including the closing paragraph.
BUT, the final 5 characters of the php line are rendered literally: '; ?>
I have tried double quotes with no change. Beats me why the terminating single quote is being ignored.
Obviously this is my gross stupidity, but I can't crack it because I simply cannot see the error in the syntax.