I need to add an extension to the php configuration. I can easily add it to the php.ini file, but I can not for the life of me find where the extension directory for the php extensions is. I looked in the php.ini file, but the directive for directory extension is commented out. However, if I look in the /etc/php5/conf.d directory, I see a series of ini file, each loading the module with nothing more than the extension= syntax. So where are those so's on the filesystem? the mysql.so? the gd.so?