On the left you have a salaried job. On the right a shoot for the moon VC startup. In between you have the entire range from trying to build products for 'passive income' on the side, to going alone starting a small cash-positive business, or freelancing. Your level of risk is entirely up to you, and the reward will usually be fairly linear, within your own earning capacity and skill set (money is fairly efficient in that sense!).
Working more hours or quitting your job fits into that scale along with all the other factors. If your appetite for risk is on the lower end such you won't quit, then you will have a harder time competing with people who've positioned themselves with more risk.
There will always be the outliers who just break the model though.
Thank you for the response. I agree, more or less. In this case, of course, I made the assumption that OP didn't want to quit his job. His skill sets are fairly common, based on what he posted. Considering that, I thought he will have a better chance of building something on the side, since getting high enough consulting rates for PHP work is hard, especially when you are trying to do it part-time. (As you said, there are outliers for this also. I assumed OP falls close to the mean/median when I wrote that.)
You make an assumption that the PHP/mySQL role consumes all of his time. That isn't necessarily true, he may be in a position where he's just tweaking scripts occasionally.
I agree that it is very difficult to find the required momentum. Some things which may help, based on my experience:
1. Divide the whole problem into subsets. Identify others who are having the same problem subsets, and partner with them to resolve them. This way, nobody has to divulge their whole business model/idea and yet can collaborate.
At the smallest level, this can be as simple as posting a technical problem on StackOverflow and participating in the discussion that follows. At a higher level, this can be something like identifying a common person to write content for multiple businesses.
2. Keeping intermediate easily reachable goals. This helps to ensure you have momentum, however small it may be. Reaching those goals also peps up your spirits, especially when you are working alone.
Edit: Those who downvoted, please provide the reason also. Happy to have a discussion. I wrote the above based on my personal experiences.