php怎么实现访问禁止

<?php 
/加IP访问限制 
if(getenv('HTTP_CLIENT_IP') && strcasecmp(getenv('HTTP_CLIENT_IP'), 'unknown')) { 
$userip = getenv('HTTP_CLIENT_IP'); 
} elseif(getenv('HTTP_X_FORWARDED_FOR') && strcasecmp(getenv('HTTP_X_FORWARDED_FOR'), 'unknown')) { 
$userip = getenv('HTTP_X_FORWARDED_FOR'); 
} elseif(getenv('REMOTE_ADDR') && strcasecmp(getenv('REMOTE_ADDR'), 'unknown')) { 
$userip = getenv('REMOTE_ADDR'); 
} elseif(isset($_SERVER['REMOTE_ADDR']) && $_SERVER['REMOTE_ADDR'] && strcasecmp($_SERVER['REMOTE_ADDR'], 'unknown')) { 
$userip = $_SERVER['REMOTE_ADDR']; 
} 
//限制ip 
if ($userip=='192.168.1.88'){ 
header("location:http://t.qq.com/wb631992791");//被禁止后跳转到微博
exit; 
} 
//限制ip段 
$ip_arr = explode('.', $userip); 
#限制的ip段，假设是192.168.*.* 
if (!(($ip_arr[0] == '192' && $ip_arr[1]=='168') )){ 
header("location:http://t.qq.com/wb631992791");//被禁止后跳转到微博
exit; 
}else{ 
header("location:http://afish.cnblogs.com");//正常IP则直接访问小鱼阁首页 
exit; 
} 
?>