Always interesting to see what code guidelines people use in what language.
Personally, I use the following for PHP: Basic Coding Standard: https://github.com/php-fig/fig-standards/blob/master/accepted/PSR-1-basic-coding-standard.md
Coding Style Guide: https://github.com/php-fig/fig-standards/blob/master/accepted/PSR-2-coding-style-guide.md