Modern PHP Coding Style

Style rules sound dull, but they decide how easily your code can be read, shared and reviewed. PHP has a widely accepted standard: PSR-12, from the PHP-FIG group.

The main rules

1. Files use <?php and no closing tag (pure PHP files).
2. Use 4 spaces to indent, not tabs.
3. One class per file, and the file name equals the class name.
4. Class names in PascalCase, methods and variables in camelCase, constants in UPPER_SNAKE_CASE.
5. Opening braces: on a new line for classes and methods, on the same line for if, loops and closures.
6. A blank line after the namespace and after the use block.
7. Keep lines reasonably short (about 80 to 120 characters).
8. Add declare(strict_types=1); after the opening tag.

A well-formatted file

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<?php

declare(strict_types=1);

namespace App\Service;

use InvalidArgumentException;

final class PriceCalculator
{
    private const TAX_RATE = 0.18;

    public function __construct(private readonly string $currency = "INR")
    {
    }

    public function withTax(float $price): float
    {
        if ($price < 0) {
            throw new InvalidArgumentException("Price cannot be negative.");
        }

        return round($price * (1 + self::TAX_RATE), 2);
    }
}

echo (new PriceCalculator())->withTax(100);

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Naming

Name things for what they are, not how they work. $users is better than $arr, and calculateTotal() is better than doStuff().

Booleans and methods

Start boolean-returning methods with is, has, can or should: isActive(), hasPermission().

Comments and docblocks

• Write a comment to explain why, not what.
• If a type is clear from the code, you do not need a docblock. Use docblocks for things the type system cannot say, such as @param string[] $tags or @throws.

Tools that enforce style

You do not need to remember the rules. Tools check and fix them.

Install them with Composer (see What Is Composer?):

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

Consistency beats perfection

If a project already has a style, follow it, even if you would choose differently. A file that matches the rest of the project is easier to read than one that is “better” but different.

The WordPress exception

WordPress has its own coding standards (tabs, snake_case function names, spaces inside brackets). When you write code for a WordPress theme or plugin, follow the WordPress standard. For everything else, use PSR-12.