Themify is a commercial WordPress theme shop. They are looking for both a freelance (remote okay) PHP developer and a frontend (Toronto based) developer. Find all the information you need on their blog post.
Page.ly is a managed WordPress hosting provider. They are looking for a primarily PHP, but also jack-of-all-trades, developer. The position is full time, and you can work remote. Learn more on their careers page.
Obox is a commercial WordPress theme shop. They are looking for a full time PHP developer. You can work remotely, but they ask that you have at least some work-time overlap with GMT+2 timezone (Cape Town), which is 6 hours ahead of U.S. Eastern Time. Learn more on their blog post.
Automattic, the parent company to WordPress.com, always seems to be hiring. Currently they’re seeking folks fit for positions from Code Wrangler to Happiness Officer. Many of the positions ask for at least some proficiency in PHP. Check out all of their openings on the jobs page.
It seems PHP, and WordPress knowledge in general, is a skill in high demand. Do you know of other well known WordPress companies hiring? Share with us in the comments.