If you know anything about php - take the job. Especially if it's one where you can choose the framework, e.g. Wordpress, Laravel, Joomla, etc...
Even if you go to school for 4 years, you won't learn as much as you will by coding on a real-world project every single day...
I recently started a job(June) and honestly I didn't know how I was going to pull everything off that my boss wanted (A beatiful site design w/ lots of CRM functionality) -- I dug into Laravel a beautiful php framework and I spend everyday in IRC chat asking for help, delving through documentation, etc...until I'm becoming pretty good at it.
Last month we moved off shared-hosting to vps hosting, something I've never done before, did we get someone else to handle the server setup? NO! I did it. I learned a lot about devops, I installed Nginx, APC, PHP-FPM, REdis.
I learned how to setup a mysql master slave replication AND how to make laravel play w/ it so that all writes go to the localhost slave, and all reads go to the maindb master.
I also have a redis server on the maindb server that is used for caching of laravel. I also had to diagnose and treat a major bottleneck(load time of 12s) -- now it's 100ms or less. (I was pulling in blog data from wordpress on every page load to integrate into the CRM -- now I cache it for 48 hours.)
Trust me I could never think of all these problems, but as I solve them I learn, and I figure out how to be a better developer, and even some devops skills --which can be very useful.
I took this job on the cheap $15/hour simply for the experience, when I finish the app to a good point as I'm the single developer, I'm planning on moving on to $40-50 an hour job, or asking for a HUGE raise. I also am working on Ruby on Rails side project in my spare time just to get some familiarity w/ that platform - the more you know.. Also I built some of the admin frontend stuff in AngularJS -- some cool filtering of orders filters as I type an email, or tracking#. So in six months I learned:
* How to setup, build, and deploy an enterprise laravel app.
* How to setup an app server cluster, with a nodebalancer duplicate the content using Csync+Lsync, Secure the system using firewalls, changing ssh logins, not allowing root logins, etc.. How to speed things up by using Nginx instead of APache - and tweak the hell out of it. How to use redis as a caching engine.
* How to use angularJS for a more dynamic front-end to my app.
* How to solve ANY problem thrown at me.
* How to test and diagnose problems w/ my app. (Learning to write better unit tests currently.)
* How to manage a mysql server cluster.
* Basic linux crap like ssh, scp, aptitude, etc...