well it might have something to do with the fact that you are using 2 sets of php tags which will be conflicting aswell as the fact that your code is wrong e.g.
by using ur code the actual page code generated would be
Code:
<?php echo
<p>Does php process below?</p>
<?php
$meee = 'hello world';
echo $meee;
?>
?>
i dont think you will be able to include php code in your articles unless you code arround it as you are echoing the artice content from inside a php function itself unless maybe its because u missed the semicolon off the end of the echo for the article, also use brackets with the echo command it is better practice i.e.
Code:
echo('some stuff to echo');