If I were you, I would try to find ways to transition my expertise. Let's face it, most managers can't gauge the abilities of a PHP expert. Many people are great at PHP, but can't cut it on other techs, so why take the hiring risk.
If, however, you could tell me a list of things you've built with Python, Ruby, etc. I would know that your stated "grasp" is probably validated. And so, by widening your expertise, you open yourself to new opportunities and prove your abilities along the way.