You may at some stage want to filter an online service based on IP address. In other words, you may want to block or grant access to a request based on their IP address. This can be handled in PHP by doing the following.

If you have the IP addresses, then it is trivial.

//First check IP address is valid
$request_ip = $_SERVER['REMOTE_ADDR'];

if ( !preg_match( "/^(([1-9]?[0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5]).){3}([1-9]?[0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])$/", $request_ip ) )
    return false;

$blacklist = array(
'111.222.12.11',
'222.111.21.22',
'221.112.11.12'
);

//check that ip is not blacklisted
if ( in_array( $request_ip, $blacklist ) )
    return false;

If you want to include a range of IP addresses, best to use a regular expression.

$blacklist_ip_range = array(
    '/^122\.244\.(\d+)\.(\d+)/', //for IP address in the range 122.244.0.0 - 122.244.255.255
    '/^123\.(\d+)\.(\d+)\.(\d+)/', //for IP address in the range 123.0.0.0 - 123.255.255.255
);

foreach( $blacklist_ip_range as $ip ) {
    if( preg_match( $ip, $request_ip ) )
       	return false;
    }

If you have a better solution, then please let me know.