[dalontano]

In 20 years in coding PHP going from the code style you described to what you want I have never seen it going well when a new tech lead comes in and wants to rewrite everything (always worked in similar settings though where human resources are limited).

This code is making $20mio, so something must be going well. Don't forget that a codebase like this covers all the history and knowledge.

So first make sure that you appreciate the work of the current team. As you write "resistance to change is huge" I would bet that the team doesn't feel like you're trying to understand them.

It actually reminds me of a client who I wrote an order system in PHP that made $15mio annually. As the client and me didn't get along anymore he was looking for someone to replace me, and found this new CTO who came in with "everything's shitty, nothing works, we need to redo everything". Obviously the client finally saw the chance of getting rid of me, only to ask me one month later to come back as they fired the new CTO. Seems like something was working all along :)