If you want to connect inside your box to the bitcoin client, then you have to use:
<?php 
   require_once 'jsonRPCClient.php';
   $coin = new   jsonRPCClient('rpcuser:rpcpw123@localhost:8332/');
   $json =$coin->getnewaddress();        
   var_dump($json);
   echo "</pre>";  
 ?>
i.e: rpchost = localhost and rpcport = 8332 (default port for bitcoin). For a different altcoin, use the provided documentation.
You previously have to enable the rpcserver with these options in your conf file.
listen=1
server=1
daemon=1
rpcuser=rpcuser
rpcpassword=rpcpw123
rpcport=8332
rpcallowip=127.0.0.1