Pros and cons of different ways of adding a real-time multiplayer game to a website on PHP

Background

The website has a classic LAMP setup and runs on a virtual private server. The aim is to add an HTML5 multiplayer game which runs on the same domain, has latency of up to 500ms, maintains state on the server side and can support a few thousand concurrent games with 2-5 players per game at peak times.

Since I had little experience with PHP and server side in general, my original plan was write a game demo in node.js+socket.io and rewrite it in PHP later on. However, now that I've written the demo (~400 lines of code on the server side) I have doubts about the plan. There are two ways of integration that I am considering:

Write the game in PHP

pros:

• Fewer changes to the original setup
• Not having to split server side into two parts in terms of languages, templates etc.

cons:

• Lack of popular solutions for real time communications in PHP
• Scalability concerns

Run node.js and PHP servers in parallel

Since the site is hosted on a VPS, I think I can put nginx in front of Apache and node.js so that the client will only have to use single port on a single domain.

pros:

• Ability to use socket.io for real-time communication with the client
• If the game server goes down, the rest of the site will still work

cons:

• complicating the setup by adding another web server and a reverse proxy

Question

As I said, I have little experience with server side, although making the demo helped a lot. Are there better ways of doing this? Did I miss out important pros/cons? Which points are the most important in practice?