I was in a remarkably similar situation, PHP dev who worked for a large UK agency. I held it out for a year, slowly refactoring the code, but the biggest proble

I was in a remarkably similar situation, PHP dev who worked for a large UK agency. I held it out for a year, slowly refactoring the code, but the biggest problem was it was a home made CMS they used, which was badly fragmented across 50 ish sites. So when I improved the code on one site, I couldn't just drop that code into all the other sites... Long story short, I quit and went freelance, best decision I ever made :) My advice to you would be that (unfortunately) it will never be considered cost effective in management's eyes to rebuild the existing sites in a decent CMS / Framework. But you should at least be able to get them to use modern dev standards on any new builds, or complete rebuild of existing sites.