php.ini in php5.2.1

Hello; I have not had the necessity to deal with php.ini files for some time. Now, because I switch from Sendmail to Postfix on one system I need to adjust the sendmail path variable. I cannot find a php.ini file in the specified location. That is not a problem because I can use ini_set(). What is puzzling is that my system, I built and installed from source on a number of different systems and seem to remember that the process creates a php.ini file. Maybe I have it wrong but in the past I seem to remember being able to find one to make sure register variables was set to off. (or maybe I ignored it because that is the default now). So, is the fact that this file is missing something I should be concerned about? PS; I have subscribed to the php-install list and get not responses to my posts, or e-mails my ISP says contain viruses, possibly from a user who requested I contact him (of her) off list. Thanks Jeff K