I've always upgraded PHP using Mark Liyange's binaries (http://www.entropy.ch/software/macosx/php - he has been away since around mid December and hasn't updated his binaries, but he says he will be back around mid January and that he will update them then. Now that this article is out I may go ahead and update it myself.) In his FAQ he says that no php.ini file is included so if you want one you should create it here:
So that's what I did and it worked fine. I don't know if this is the proper location if you follow the instructions in this article.
Another idea is to create a PHP file containing only:
<?php phpinfo() ?>
View this file in your browser. At the top in the first table you will see a cell labled "Configuration File (php.ini) Path". Check the path it gives in the next column over. If your php.ini file is not there then try creating one in that location.