php获取客户端ip get_client_ip()

function get_client_ip(){
if (getenv("HTTP_CLIENT_IP") && strcasecmp(getenv("HTTP_CLIENT_IP"), "unknown")){
　　$ip = getenv("HTTP_CLIENT_IP");
}else if (getenv("HTTP_X_FORWARDED_FOR") && strcasecmp(getenv("HTTP_X_FORWARDED_FOR"), "unknown")){
　　$ip = getenv("HTTP_X_FORWARDED_FOR");
}else if (getenv("REMOTE_ADDR") && strcasecmp(getenv("REMOTE_ADDR"), "unknown")){
　　$ip = getenv("REMOTE_ADDR");
}else if (isset($_SERVER['REMOTE_ADDR']) && $_SERVER['REMOTE_ADDR'] && strcasecmp($_SERVER['REMOTE_ADDR'], "unknown")){
　　$ip = $_SERVER['REMOTE_ADDR'];
}else{
 $ip = "unknown";

}
return($ip);
}