How do I include an image in PHP?

Hi. I'm new here and don't know much PHP.
Anyways I want to create an avatar with a random image:

<html>
<body>
<img source="http://www.php-enabled-server.com/foo.php">
</body>
</html>

<?php
 (random image code here)
 include($random_img);
?>

How can I get this thing to work? I tested this with a specific one image but it didn't work.

well you cant use include to include an image file i dont think but it does seem practical

Now there are two otherways of doing this

There the database way
you the phpfile as like config which puts all of them in an array or something and then rand() randomise them all