PSR-12 Coding Standard

Also Known As

TL;DR

Explanation

PSR-12 (accepted 2019) extends and replaces PSR-2, building on PSR-1. It specifies: files must use Unix LF line endings and end with a blank line; 4-space indentation; lines up to 120 characters (soft limit 80); one blank line between use declarations and class body; opening braces for classes and methods on their own line; no space before parentheses in control structures. Most PHP projects enforce PSR-12 via PHP_CodeSniffer or PHP-CS-Fixer in CI pipelines.

Common Misconception

Why It Matters

Common Mistakes

• Not using an automated formatter (PHP CS Fixer) — manual PSR-12 compliance is inconsistent.
• Braces on the same line for class and function declarations — PSR-12 requires them on the next line.
• Missing blank lines between method declarations.
• Not enforcing PSR-12 in CI — the standard degrades without automated enforcement.

Code Examples

<?php
class Foo{
public function bar($x,$y){
if($x){return $y;}
return null;
}}

// PSR-12 compliant:
class Foo
{
    public function bar(int $x, int $y): ?int
    {
        if ($x) {
            return $y;
        }

        return null;
    }
}

<?php

declare(strict_types=1);

namespace App\Domain\Order;

use App\Domain\User\User;
use DateTimeImmutable;

class Order
{
    public function __construct(
        private readonly int               $id,
        private readonly User              $customer,
        private readonly DateTimeImmutable $placedAt,
    ) {
    }

    public function getId(): int
    {
        return $this->id;
    }
}

Tags

Related Terms

References

• https://www.php-fig.org/psr/psr-12/
• https://github.com/squizlabs/PHP_CodeSniffer