To be honest, I have developed an online browser based game and worked on a previous browser based game, both written in PHP. Neither were successful, but I don't think that is the point of developing an online browser based game. Above all, the goal should be to have fun and create a fun game. If you so happen to make money off of the game, then all the better. I had wanted to start a series and got up to user management. Really, the details were more abstract than I would have liked. The page is one of my most popular pages. I think the problem was that I started the series at a point where I assumed the reader had an abstract of the game, planned out the details, knows what the game is going to be, etc. Building a game doesn't start at the coding stage and I think that is where I made my mistake. Any PHP programmer can develop a PHP game. It is similar to any other PHP web application, except the forms interact and modify what other visitors are seeing and the data persists for all visitors. The coding can be as simple or complex as you are capable of developing.
A well developed game, takes imagination and planning. The more planning the better the initial iteration of the game will be. I think some people make the mistake of thinking that you have to develop every aspect of the game before entering production. Certainly, if you were developing a game for a group of programmers at a company like EA, then yes, you'd want to do that. The problem is often one of motivation and it depends on how motivated you will be spending weeks or months designing the game.
The other problem, and I think agile project management helps out vastly in this area, is actually developing a plan that can be implemented. A novice programmer is not going to be able to put together a SVG canvas or WebGL project overnight, unless that person is extremely motivated and intelligent or has a ton of help from an experienced programmer. I suppose the point I'm trying to make, is that I've written many of designs that just weren't implemented, because my vision wasn't possible at that time.
What does it mean when what you designed is not possible? It simply means that you need to work around the limitations until later. Be creative. There are many solutions to difficult problems.
Farming Sim Example
I have a game that I've been designing for a while now. The reason I haven't yet developed it is because I'm not experienced enough to pull it off. The problem is that I want to design the game to where you have an near infinite land mass for planting crops and placing buildings and whatever else will be in the game. I wish to have this to be graphical and where you can place the elements visually. One solution that I've had for a while is to have it all text based. You have crops, buildings, etc and you simply set a quantity. The crops, buildings, etc have a predefined area that they take up and once you've filled your current land, you will not be able to make any more purchases.
I could implement this basic solution now. The reason I have no desire to, is that it wouldn't be fun for me. I don't want to a game where it is text-based. I want to play my game graphically and so I will not implement a simple idea to rush this game out. If I were to do it for the money, I would attempt to do it. However, this is not 2000s or pre-Flash and Facebook game. The problem is that if I were to do a text-based game like this, I doubt many people would choose to play the game over Farmville or another similar game.