The bug is the same as: http://bugs.php.net/bug.php?id=8638
But is still there in php-4.2.1 and 4.1.2 on various apache/linux platforms.

Try this:
Create a .php-file with chmod 644, open it in your browser.
It'll work.
chmod it to 000, and you'll give you a "Warning: Failed opening '/path/to/file.php' for inclusion (include_path='') in Unknown on line 0"

Then try a .html-file, chmod 644, chmod 000 etc.
Will give a nice 403 error message.