Honestly I warn: take this text with a certain amount of skepticism. I just recently started to get acquainted with the internals of PHP, but I would like to tell you about what is happening behind the scenes bug # 75237 .
These are the principles of software development, taken from the Robert Martin Clean Code book and adapted for PHP. This manual is not a programming style, but to create a readable, reusable and refactoring-friendly PHP code.
Not each of these principles should be strictly observed, and with even fewer will all agree. These are just recommendations, not more, but they are all codified in the author's many years of collective experience.