If you do #1, you'll get #3 and #4 for free, and full integration of #2 and #6 :-) Best 80 bucks you can ever spend if you write PHP.

My basic procedure when inheriting legacy code is:

- Load the project in phpstorm

- Perform autoformatting so it becomes readable

- Run code inspection to find any obvious issues the original author missed

- Write tests in phpstorm, if not already exists

- Run the code with xdebug, step through it