php实现禁止IP段访问网站的代码

<?php
//加IP访问限制
if (getenv(&#39;HTTP_CLIENT_IP&#39;) && strcasecmp(getenv(&#39;HTTP_CLIENT_IP&#39;) , &#39;unknown&#39;)) {
    $userip = getenv(&#39;HTTP_CLIENT_IP&#39;);
} elseif (getenv(&#39;HTTP_X_FORWARDED_FOR&#39;) && strcasecmp(getenv(&#39;HTTP_X_FORWARDED_FOR&#39;) , &#39;unknown&#39;)) {
    $userip = getenv(&#39;HTTP_X_FORWARDED_FOR&#39;);
} elseif (getenv(&#39;REMOTE_ADDR&#39;) && strcasecmp(getenv(&#39;REMOTE_ADDR&#39;) , &#39;unknown&#39;)) {
    $userip = getenv(&#39;REMOTE_ADDR&#39;);
} elseif (isset($_SERVER[&#39;REMOTE_ADDR&#39;]) && $_SERVER[&#39;REMOTE_ADDR&#39;] && strcasecmp($_SERVER[&#39;REMOTE_ADDR&#39;], &#39;unknown&#39;)) {
    $userip = $_SERVER[&#39;REMOTE_ADDR&#39;];
}
$ban_range_low = ip2long("217.0.0.0"); //ip段上
$ban_range_up = ip2long("217.255.255.255"); //ip段尾
$ip = ip2long($userip]);
if ($ip > $ban_range_low && $ip < $ban_range_up) {
    print "Banned";
    exit();
}