I was in the same position as you but replace PHP with Java.
I thought I didn't need a degree but then met people in the industry that I wanted to be like, but I was limited by not having a degree.
It wasn't possible for me to study full time and I didn't really want to as I wanted to continue to have my years of work experience growing, so I signed up for a part time course.
Two years before my degree was finished I was nearly passed over on a job because I didn't have a degree so it really encouraged me to get it finished.
With the last round of job interviews there are many that said I would not be being considered without the degree.
If I were back in that same position again, I'd choose to do it the same way. Your relevant work experience keeps growing but you still get a degree - it's hard work and long hours but I think it was worthwhile.