What is the correct syntax for this?

I've seen:

php_value include_dir .:/usr/home/blah/include_dir

php_value include_dir ".:/usr/home/blah/include_dir"

php_value include_path .:/usr/home/blah/include_dir

I'm trying to put this in an htaccess file so I can just include files without having to specify the relative path. Does the apache server need to be setup in a certain way to allow for this?

Edit: It's the bottom one