The Laravel News site has a new post sharing the application of "clean code" concepts to PHP with a few handy examples. These suggestions are pulled from this set of guidelines.
Clean Code PHP (jupeter/clean-code-php), is a guide based on the book Clean Code: A Handbook of Agile Software Craftmanship, a classic programming book about writing maintainable code by Uncle Bob Martin.The clean-code-php guide is inspired by a JavaScript adaptation, clean-code-javascript with PHP-specific features.
Examples they show in the post are around unneeded context, the number of function arguments and functions doing more than one thing. They also include a word of warning about these and other "clean code" suggestions, pointing out that they're mostly matters of opinion and not hard and fast rules to enforce every time. The post ends with links to two "clean code" resources for more reading: "[Clean Code]"(https://amzn.to/2wFCjo4) and "The Clean Coder: A Code of Conduct for Professional Programmers".