简单获取并验证client ip

function get_ip_address() {
	foreach (array('HTTP_CLIENT_IP', 'HTTP_X_FORWARDED_FOR', 'HTTP_X_FORWARDED', 'HTTP_X_CLUSTER_CLIENT_IP', 'HTTP_FORWARDED_FOR', 'HTTP_FORWARDED', 'REMOTE_ADDR') as $key) {
		if (array_key_exists($key, $_SERVER) === true) {
			foreach (explode(',', $_SERVER[$key]) as $ip) {
				$ip = trim($ip);
				if (filter_var($ip, FILTER_VALIDATE_IP, FILTER_FLAG_NO_PRIV_RANGE | FILTER_FLAG_NO_RES_RANGE) !== false) {
					return $ip;
				}
			}
		}
	}
}