Linters are a great way to keep your project clean and remove any code cruft.

In our projects we include several static analysis linters.

PHP

PHP_CodeSniffer

PHP_CodeSniffer is a script that will tokenize your PHP files and based on selected rulesets, detect violations of set coding standards.

It also includes the phpcbf script that will automatically correct coding standard violations when possible.

It can tokenize and check JS and CSS, but we don't use it for checking those file types.

PHPCS doesn't know about context. It just tokenizes your code, and checks that tokenized code against sniffs. Sniffs are just rules that will check if tokenized code is valid. For instance if you disallow Yoda conditions, tokenized code will look different for

if ('yes' === $someCode) { //... }

vs

if ($someCode  === 'yes') { //... }

PHPStan

PHPStan is a static analysis tool that will parse your code (not tokenize like phpcs), and try to infer types that go in your code and out of your code, either from doc-blocks or arguments, and warn you if something is off. For instance, passing integer from one function to another function as argument when the expected argument type is a string.

It does what compilers do in compiled languages like Java, but faster, and you can configure it or extend it.

Because of that, it goes perfectly with PHPCS. Since it can understand context it's an essential tool for preventing bugs that can happen by type juggling for instance.

JavaScript

For JS linting we are using ESLint. It's a static analyzer. It works similarly to PHPStan, parsing code to abstract syntax tree (AST) and finding patterns in code.

SCSS

For SCSS files we are using Stylelint. It's a style sheet linter written in JS useful to finding scss inconsistencies and errors.

Running linters

You can run individual linter or all of them at once.

Once you've set up a project, you'll have npm and composer scripts at your disposal. Running

npm run lint

will run JS, CSS and coding standards check.

You have individual npm checks:

npm run lintJs
npm run lintStyle

For composer checks you can run:

composer test:types // PHPStan
composer test:standards // PHPCS

Note: These scripts can be renamed in your project.