There is a way out of this mess. It is not straight forward though. There are two ways: 1. Convince the business team that these team members might leave and p

There is a way out of this mess. It is not straight forward though. There are two ways: 1. Convince the business team that these team members might leave and put the $20mn revenue at risk. There is no way you can make them learn and do things properly. Therefore, take separate budget, hire a new separate team. Do full rewrite of backend and plug the app and new website into it. It would be 1-2 year project with high chance of getting failed (on big bang release...stressful and large chance of you getting fired but once done you can fire the oldies and give the business team a completely new setup and team) or partial failed (that means large part of traffic would move to new system but some parts would remain...making the whole transition slow, painful and complex plus never ending). 2. Add newer strong and senior php members to the existing team. Ask new senior members to not fight with them but train them. They would listen to them as these guys would know more. Slowly add version control, staging-dev envs, add php framework for new code, add caching, CI/CD pipeline, bring on a automated test suite built by external agency etc. This would be low risk as business team would see immediate benefits/speedups. Rewrite portions of code which are too rusty and remove code bases which do not required anymore. This would be possibly take 5-6 years to complete, giving you ample job security while achieving results in a stable manner.