Method Could Be Static

ID

php.method_could_be_static

Severity

info

Remediation Complexity

medium

Remediation Risk

low

Remediation Effort

medium

Resource

Code Smell

Language

Php

Tags

best-practice, code_smell

Description

Reports an instance method whose body never touches the object context — it references neither the $this pseudo-variable nor a parent:: member — and could therefore be declared static.

Rationale

A method that never reads or writes instance state is a pure helper that happens to live on the class. Declaring it static documents that intent: callers see it does not depend on a particular object, the engine need not bind $this, and the method can be reused without constructing an instance. Leaving such a method non-static is a mild code smell that hides the routine’s true nature and invites needless object creation.

Magic methods (construct, get, __toString, …) are invoked by the runtime on an instance and are never reported; abstract and interface methods have no body to analyse and exist to be overridden, so they are skipped too. A $this used inside a closure declared in the method counts as using the instance, because such a closure binds the enclosing $this.

<?php
abstract class Calculator
{
    private int $base;

    public function add(int $a, int $b): int   // FLAW — no $this / parent::, could be static
    {
        return $a + $b;
    }

    public function withBase(int $a): int       // OK — reads $this->base
    {
        return $this->base + $a;
    }

    public function withParent(): int           // OK — calls parent::
    {
        return parent::compute();
    }

    public static function already(int $a): int // OK — already static
    {
        return $a * 2;
    }
}

Remediation

If the method genuinely does not need an instance, add the static keyword and call it via ClassName::method() (or self::method() / static::method() from inside the class). If a dependency on instance state was intended but accidentally omitted, add the missing $this→ reference instead.

References