PHP.ini is not related to user accounts I believe, but to the server itself. What you need to do in php.ini?
Anyway, I suggest you to send a ticket describing exactly what you need.
You can also check out here http://server18.000webhost.com/phpinfo.php for the overall configurations. Just see what your server is in your account information. But I believe that they are all set in the same way.
You won't be lucky, I guess. Those are restrictions imposed and not just casual, it's free hosting you know . They will suggest you to upgrade your account to their paid hosting. If you want to do so http://www.000webhost.com/upgrade
Well you can do so, I'm only on doubt if you can only enable modules or if you can also set values, but try it. You won't lose anything
If you do that successfully great, if not send a ticket, or maybe someone around the forum can enlighten you a bit further.