You can use get_cfg_var('cfg_file_path') for that:
To check whether the system is using a configuration file, try retrieving the value of the cfg_file_path configuration setting. If this is available, a configuration file is being used.Unlike phpinfo() it will tell if it didn't find/use a php.ini at all.
var_dump( get_cfg_var('cfg_file_path') );
And you can simply set the location of the php.ini. You're using the command line version, so using the -c parameter you can specifiy the location, e.g.
php -c /home/me/php.ini -f /home/me/test.php