PHP doesn't use php.ini

When i installed PHP, I had written to my httpd.conf PHPIniDir "c:/php". But phpinfo() returns "C:\WINDOWS" in "Configuration File (php.ini) Path" row and right path to my php.ini in "Loaded Configuration File". It looks like php.ini really isn't used. I think so because when i try to enable MySQL it doesn't work ("extension=php_mysql.dll", "extension=php_mysqli.dll" and "extension=php_pdo_mysql.dll" is uncommented, "extension_dir" is correct, libmysql.dll is copied to C:\WINDOWS\system32). I've tried to write to php.ini an abracadabra. But I havent received an error as i expected. I've tried to rename php.ini. phpinfo() has returned "(none)" in "Loaded Configuration File" row instead of "c:\php\php.ini" as that was before. But PHP still worked. It worked without php.ini. It seems very strange. I've searched another php.ini on my system. There is no another one. What's wrong? Why doesn't PHP use php.ini file?