Well, I've whitelisted the IPs in question, set server=1, everything else I can think of. But but but but but, what's this about PHP libraries? I uploaded phpRPCClient.php and Bitcoin.php and have been trying those.. Are you saying I actually have to install a system library too? Well, I didn't install any libraries. What do I need to do? "sudo apt-get php-json"?
No, I just meant to check that you're passing the right username, password, IP, and port to your JSON library.
You could try Xenland's suggestion, if you're running bitcoind, you don't need the sever flag (I have no idea why that might be a problem).
For reference, this is my full bitcoin.conf, and it lets me connect from other computers on the network:
(You don't want the testnet flag set.)
From the computer you're running the php on, you can try running:
telnet 192.168.1.2 8332
Replacing 192.168.1.2 with your IP, and 8332 with your port if you changed it.
If it gives you a connect error, your bitcoind is configured wrong, or you have the wrong port/ip address.
If it just sits there waiting for input, you're having a username/password issue.