I make money with PHP because the company I work for pays me. It sounds boring and conventional, but every 2 weeks, I get a nice paycheck.
I've been a contractor, and did well enough with it.
Web technologies are changing extremely quickly.
The cost to get into the field is virtually nil, however, to excel and succeed, you have to work hard and do a good job. If you can find a way to receive recurring payments, you may be able to leverage your work into the future, but there is enough code already out there that you need a team to build something robust enough to really profit. Then, you need to decide what your hourly rate is and whether it's worth it.
Ideas:
* If you have strong server skills, you could be a hosting reseller.
I don't know what the margin is on this, competition is steep. Hosting is cheap.
* You could run your own web company, and get the recurring income from hosting your sites
Managing customers can be difficult. Most people don't understand the work that goes into a good site.
Design is important, for me, making page 'pretty' is difficult.
* You could create an <acronym title="Search Engine Optimization"><acronym title="Search Engine Optimization">SEO</acronym></acronym> service, and have the clients pay a fee based on the traffic increase.
* Affiliate marketing and PayPerClick ads may be profitable
* Run a free cart system and take a portion of the sales for payment.
There is so much free software it's difficult to create something valuable enough people are willing to pay for it.
I think the next boom will be mobile applications, connecting people to the 'net through their smart phones.