Open Source PHP VPN Software for Windows

CacheGuard Gateway is a free and open-source Unified Threat Management (UTM) solution, a Web Application Firewall (WAF), and a Quality of Service (QoS) platform designed to optimize WAN traffic. To obtain a CacheGuard Gateway appliance, download CacheGuard-OS and install it on the bare-metal or virtual machine of your choice. It’s that simple and completely free. The UTM includes a firewall, web antivirus, VPN server, and a URL-filtering and SSL-inspection web proxy. The WAF operates in conjunction with a reverse proxy, web application load balancer, and SSL offloader, and is capable of blocking malicious requests as well as traffic from IP addresses with poor reputations. The QoS manager enables traffic shaping to prioritize critical network flows, load balance multiple WAN links, and cache web traffic.

Lomalarga is a port forwarding (VPN-like) service based on SSH & Linux. Based entirely on open source. The client is written in C# and the administration is based on Linux/lighttpd/PostgreSQL/PHP, with the UI written with Google Web Toolkit.

M0n0wall currently doesn't support IPSEC VPN where one or both ends are dynamic IP addresses. This PHP script along with the dynamic DNS service built into m0n0wall, auto-updates the remote gateway IP address in the VPN configuration.