PHP获取当前用户真实IP的方法

function getIp(){
	$onlineip='';
	if(getenv('HTTP_CLIENT_IP')&&strcasecmp(getenv('HTTP_CLIENT_IP'),'unknown')){
		$onlineip=getenv('HTTP_CLIENT_IP');
	} elseif(getenv('HTTP_X_FORWARDED_FOR')&&strcasecmp(getenv('HTTP_X_FORWARDED_FOR'),'unknown')){
		$onlineip=getenv('HTTP_X_FORWARDED_FOR');
	} elseif(getenv('REMOTE_ADDR')&&strcasecmp(getenv('REMOTE_ADDR'),'unknown')){
		$onlineip=getenv('REMOTE_ADDR');
	} elseif(isset($_SERVER['REMOTE_ADDR'])&&$_SERVER['REMOTE_ADDR']&&strcasecmp($_SERVER['REMOTE_ADDR'],'unknown')){
		$onlineip=$_SERVER['REMOTE_ADDR'];
	}
	return $onlineip;
}