Mutable global state (ARCH7187)

Key php.quality.mutable-global-state · Severity warning · Category quality

Mutable global or static state creates hidden dependencies, breaks testability, and can leak across requests. Move the state into instances or make it constant.

Incorrect

<?php
class Config
{
    public static array $settings = [];
}

Config::$settings['debug'] = true;

Correct

<?php
final class Config
{
    public function __construct(private readonly array $settings) {}

    public function get(string $key): mixed
    {
        return $this->settings[$key] ?? null;
    }
}

Fix

Move shared state into an injected instance, or make it immutable (readonly).