Jacob Santos was having a problem with the Zend Framework. It couldn't find its own files. So, he's come up with a hack that helps mod_php users to avoid the problem.
I've had problem with Zend Framework not being able to find its files, which is usually not good. The "workaround" of adding the realpath works, but would be overwritten when updating. Besides, going through the files just to add realpath locations is a hassle.
The php_value only works with mod_php, so good luck if you are running PHP using CGI/FastCGI. Actually, you'll have no luck, because it won't work using CGI.