Direct access to the database is quite simple.
You can install a firebird server and PHP with interbase extensions. If you have CPanel or other server management tools on the internet site, this should be very easy. If not, there's probably an .rpm for it somewhere.
If all you do is 'select' statements, it would be fairly simple to program (no api required) and would keep the database from being corrupted. The downside is that you have to upload the whole database every so often to keep it current.
On my home (windows vista) system, I'm using php as a stand-alone and a firebird server. This works just fine...php has access to the database and to the internet. For me, that means I can collect data from the internet and add it to the database from a command-line script. At some point, I'll probably build a gui for this, but time isn't something I have lots of at the moment.