Setting PHP Include Dir

Hi, I'm trying to set a PHP include directory for one of my sites. I'm on a shared hosting system, so I don't have access to the php.ini file. My plan was to do it using a .htaccess file in Apache - however I must be doing something very much wrong, as it isn't working. Here is what I've tried: php_value include_dir = ".:/data/sites/site_name/htdocs/includes" I've checked the above path by running phpinfo(); on my site to determine where its located on my servers hard drive. When I add the above line to my .htaccess file - I get a 500 Internal Server Error. My site is using Apache 1.3.12 and PHP 3.0.18, any thoughts on how I might get this to work? Thanks -Tim