Setting PHP Include Path on a per site basis?

Question

I can set the PHP include path in the php.ini:

include_path = /path/to/site/includes/

But then other websites are affected so

Answer 1

Why do you think append to include path is bad practice?

This code near top of root script shouldn't be that bad...

$path = '/path/to/site/includes/';
set_include_path($path . PATH_SEPARATOR . get_include_path());

IMHO the main advantage is that it's portable and compatible not only with Apache

EDIT: I saw a drawback of this method: small performance impact. see http://www.geeksengine.com/article/php-include-path.html