README

PHPStan rule to enforce readonly usage on properties and classes when safe to do so.

Description

This PHPStan rule analyzes code detecting properties and classes that can be safely declared as readonly. The goal is to help improving code safety and predictability by leveraging PHP's immutable properties feature.

Use it in static analysis to easily spot where you can apply readonly and make the code more robust.

Features

• Detects properties and classes that can be safely declared as readonly.
• Ensures that readonly properties are not overwritten.
• Supports both traditional and PHP 8.0+ promoted properties.

Limitations

• Does NOT support traits yet: The rule currently does not handle properties or classes using traits, so results may be inaccurate in those cases, but it still be usable.

Installation

Add the rule to your PHPStan setup via composer (or include the file directly if standalone):

composer require --dev sal/phpstan-readonly-enforcing

Configuration

Add the rule to your phpstan.neon:

rules:
	- Sal\PhpstanReadonlyEnforcing\Rules\EnforceReadonlyRule

Example

<?php

class Test
{
    private string $name;  // If never modified after construction, can be readonly
    private readonly string $email; // Same here
}

class SecondTest // Both properties are readonly, so the class can be readonly
{
    private readonly string $name;
    private readonly string $email;
}

readonly class ThirdTest
{
    public function __construct(
        private readonly string $name,
        private readonly string $email,
    ) {
        $this->name = 'test'; // Error, cannot be overwritten
    }
}