Go with what works
Error messages should contain the information that caused the error. Your average Microsoft error "error 37253" is worthless to me
Keep functions or methods short. Anything longer than 20 - 50 lines is likely too long
Comment why is happening, not what
PHP is actually a really nice language to work with both for web and command line utils
Don't over engineer, KISS. Keep It Simple Stupid
SOLID is quite okay but sometimes there are solid reasons to break those rules
MVC is a PITA in practice, avoid it when possible