PHP Coding Standards and Tools

A coding standard is an agreed set of style and quality rules. The point is not that the rules are perfect, but that everyone follows the same ones, so code looks the same and reviews focus on logic.

You already know the PSR-12 style from Modern PHP Coding Style. This lesson is about tools that enforce standards, so you do not have to remember them.

The standards you will meet

EditorConfig

A small .editorconfig file makes every editor use the same indentation and line endings.

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root = true

[*]
charset = utf-8
end_of_line = lf
insert_final_newline = true
trim_trailing_whitespace = true

[*.php]
indent_style = space
indent_size = 4

Style checkers and fixers

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composer require --dev squizlabs/php_codesniffer
vendor/bin/phpcs --standard=PSR12 src/
vendor/bin/phpcbf --standard=PSR12 src/

Static analysis

Static analysers read your code without running it and find mistakes: calling a method that does not exist, passing the wrong type, using an undefined variable, dead code.

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composer require --dev phpstan/phpstan
vendor/bin/phpstan analyse src --level=6

Start at a low level and raise it as you clean up. Static analysis is a very cheap way to find bugs before users do.

For example, this code has a bug that no test needs to run to find:

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<?php
function total(array $items): int
{
    return array_sum($items) . "";   // PHPStan: should return int, string given
}

Syntax check

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php -l file.php

Checks a file for syntax errors without running it. A one-liner for a whole project:

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find src -name "*.php" -print0 | xargs -0 -n1 php -l

Tests

Style and static analysis do not prove the code is correct. Automated tests (PHPUnit or Pest) do. Even a few tests on your most important logic catch regressions.

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<?php
function slugify(string $text): string
{
    return trim(preg_replace("/[^a-z0-9]+/", "-", strtolower($text)), "-");
}

// A tiny self-check, the seed of a real test
$cases = [
    "Hello World" => "hello-world",
    "  PHP & MySQL!  " => "php-mysql",
    "Already-slugged" => "already-slugged",
];

foreach ($cases as $input => $expected) {
    echo slugify($input) === $expected ? "ok " : "FAIL($input) ";
}

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ok ok ok

Run the checks automatically

A minimal composer script keeps the commands short:

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{
    "scripts": {
        "lint": "phpcs --standard=PSR12 src",
        "analyse": "phpstan analyse src --level=6",
        "test": "phpunit",
        "check": ["@lint", "@analyse", "@test"]
    }
}

Run composer check before you push.

Adopt a standard, then stop arguing

Choose one, write it down (a CONTRIBUTING.md helps), let the tools enforce it, and spend review time on design and correctness.