What is the fastest method for changing php settings (save php.ini)?

I'm sorry if this question has been answered before, but I couldn't find anything in the archives. I don't have access to php.ini and I was wondering which method for changing settings is the fastest. Take, for example, "session.cache_expire". This can be set via ini_set(), session_cache_expire(), or in .htaccess. I have a handful of session- related settings that need to be set with each script and with that in mind, would it be faster to have .htaccess do the work or would ini_set be the optimum method? And what of those, like "session.cache_expire", that have specific function that can be used? Thanks ahead of time for any help.