There are 2 ways to do this I've recently discovered:
First, use the highlight_file command thus,
highlight_file('hello.php');
Second, allow .phps files. To do this (I'm using an Ubuntu Apache on local host here), go to the file /etc/apache2/mods-available/php5.conf
Change the line highlighted in red to the one highlighted in blue
<FilesMatch ".+\.phps$">
SetHandler application/x-httpd-php-source
# Deny access to raw php sources by default
# To re-enable it's recommended to enable access to the files
# only in specific virtual host or directory
Order Deny,Allow
Deny from all
Allow from all
</FilesMatch>
Now, if you rename hello.php to hello.phps and display it in your browser, it will show as PHP code.
Hope this helps.
