A quick little Access Control List (ACL) snippet I made for PHP/HTML. Enjoy!

<?php

$acl = array(
    // Populate with IP/Subnet Mask pairs.
    // Any zero bit in the subnet mask acts as a wildcard in the IP address check.
    array("192.168.10.24","255.255.255.255"),
);

$acl_allow = false;
for ($i = 0; $i < count($acl); $i++) {
    $ip2chk = (ip2long($acl[$i][0]) & ip2long($acl[$i][1]));

    if ((ip2long($_SERVER['REMOTE_ADDR']) & $ip2chk) == $ip2chk) {
        $acl_allow=true;
    }
}

if ($acl_allow) {
    // Put all test stuff here!! Only visible to ACL.
    phpInfo();
} else {
    echo "<a href='http://this-page-intentionally-left-blank.org/whythat.html' target='_blank'>This page intentionally left blank.</a>";
}

?>