The problem with just doing a search is that there can often be multiple versions of php.ini around. Especially in multi-user environments. To find out where your specific php.ini is:
php5 -i | egrep "php.ini"
Configuration File (php.ini) Path => /etc/php5/cli
Loaded Configuration File => /etc/php5/cli/php.ini
Of course in Windows you'll probably not have any grepping tools, unless you've installed them manually so something like:
and then you can load the text file into an editor and search for php.ini