The TCP wrappers provides a classical Unix mechanism which has been designed to check if the remote client is able to connect from the given IP address.
Tcpwrap is currently available through PECL » http://pecl.php.net/package/tcpwrap.
If » PEAR is available on your *nix-like system you can use the pear installer to install the tcpwrap extension, by the following command: pear -v install tcpwrap.
You can always download the tar.gz package and install tcpwrap by hand:
Example#1 tcpwrap install by hand
gunzip tcpwrap-xxx.tgz
tar -xvf tcpwrap-xxx.tar
cd tcpwrap-xxx
phpize
./configure && make && make install