Yes, much of the work I need is php involved. I guess you could go the other way and look at asp or .net.
I guess it largely depends on what you have an interest in and skill.
No matter what you learn you are better served than spending that time not learning.
Go to some freelancing sites(and here) and see what jobs people need. Look for the ones that interest you, and look for the skills you dont have in order to get your next gig.