Yet another php.ini question

Firstly, apologies for having to ask about this; I’m sure it’s sitting right in front of my face on the wiki or KB or site(s) somewhere, so this is just as much a “need another set of eyes” as much as anything. Ocular rental fees may be negotiated in terms of pints of beer for anyone living/visiting in the slightly northeasterly of Philadelphia area.

I have my very own CGI PHP5 compilation running quite nicely; thanks to all who contributed KB and wiki in that regard.

And without futher adieu:
I can’t seem to wrap my poor little brain around how to get PHP to see different php.ini files within each separate domain; in spite of the presence of a perfectly good php.ini in the root directory of the respective HTML, PHP stubbornly resists all such effort to reconfig even the most innocuous of settings (PHP default session id, frex) and insists on using the default in the …/etc/php5/ directory.
Is this a simple sorta missing “allow override” thing or do I need to recompile?
Current “phphinfo” online @ default page.
Many thanks in advance for any kick in the right direction.

According to one of the documents that came with the windows version, the location of the ini file is a compile option.