If you're talking localhost server, then it will be wherever the server is.
But as you say "FTP" I'm guessing you're talking hosted online server.
And if it's a shared host, it's very unlikely you will be able to get at the ini file directly yourself. They're kept outside of the individual site directories and neither HTTP nor FTP can get at them. This is something you need to discuss with the hosting provider.
That said, is it something you can deal with using .htaccess or ini_set() ??