The FIG standard that forbids TAB for indentation (which is perfectly legal in PHP), the notion that classes should be either abstract or final, the micro-optimizations (thou must use single quotes, things like that).
I don't think anyone can tell anyone how to write PHP, because nobody knows how to get it right (myself included). Yet in my many years of coding in PHP, there's been more and more tooling and so-called "standards" that do exactly this.