Following a LPT from /r/programming, I'm trying video game soundtracks, which are supposedly designed to help you concentrate on the task at hand, whether that's grinding or a boss fight. No guarantee that you'll get the boss fight song when you're in the middle of something difficult, though, so YMMV.
You're quite welcome, best of luck. Also, I didn't mean to suggest that you should move away from PHP, only that you should add other technologies to your toolbox. PHP experience is and will continue to be valuable, no matter what the 20-something brogrammers say.
Google for a list of web design/development agencies in your area, and they should have jobs listed on their sites, which will let you know who's looking. Ignore the instructions for applying online and try to meet someone from the firms you're interested in, maybe at a meetup/drinkup/etc. If you want to be really guerilla, set up shop in a coffee shop near their offices for a couple of days and see if you can spot a couple of their employees, then strike up a conversation.
A portfolio will really help here. If you can put together a small site that shows what you've done before, that will help. The Drupal agencies (the better ones, anyway) will also probably want to see some activity on Drupal.org, but that's not necessarily a deal-breaker. If you do want to work on Drupal, go to some Drupal meetups, and make it your goal to be ready to apply for a Drupal job at the next DrupalCon in Austin next year (Drupal has a learning curve, you will need the time).
I started my career as a developer by learning PHP over a decade ago, it's still the language I know best, and I was even Zend certified at one point, but I don't describe myself as a "PHP dev," and neither should you. You're a developer, and most of your experience is in PHP. It's a subtle, but important difference.
I'm going to advise you to diversify your skillset, but first, if you really want to stay within the PHP world, find an agency (or start your own) that does a lot of work with either Drupal or Wordpress. They're not corporate, and there are plenty of them.
If you really want to get "unstuck," learn something new. Here's what you're going to do: find a hackathon that takes place a month from now (see http://www.hackathon.io/ or ask Uncle Google), and register for it. Then spend the next month learning Android, AngularJS, Backbone.js, Python, Rails, or whatever your hackathon is based on, and then go to the event and use it.
Given that you already have a job as a developer, there's no reason for you to be unemployable, ever. If you have a corporate job now, I have a hard time imagining that you don't have some slack in your day that you could devote to trying out Android or AngularJS, as julianpye suggested; or Backbone.js, or Python, or Rails, or whatever. If you can't find the time at work, throw your TV off the roof of your house/apartment building and spend an hour or two on it at night.
Come back next month and if you're still stuck, post again and we'll talk. (But I'm pretty sure you won't be stuck.)
Create an "Identity" for general stuff, and tag everything else with [startup name]. Done.