PHP, MySQL dev is my main job. I have a lot of experience coming into small businesses and refining their processes to increase efficiency and increase (double in one case) revenue.
If you're talking about increasing revenue from a CRO perspective, then becoming a CRO consultant could be a solution. patio11 publicly claimed to be making $30k a week before he quit.
I'd recommend you to learn new skills. Even though there's lots of PHP/MySQL jobs, newer tech might pay better (like Node.js and NoSQL databases, maybe AngularJS on the frontend side).
