Error Identifier: impurePropertyHook.pure

← Back to impurePropertyHook.*

Every error reported by PHPStan has an error identifier. Here’s a list of all error identifiers. In PHPStan Pro you can see the error identifier next to each error and filter errors by their identifiers.

Code example #

<?php declare(strict_types = 1);

final class Foo
{
	private int $backing = 1;

	public int $value {
		/** @phpstan-impure */
		get => $this->backing; // ERROR: Get hook for property Foo::$value is marked as impure but does not have any side effects.
	}
}

Why is it reported? #

A property hook (PHP 8.4+) is marked as @phpstan-impure, but PHPStan’s analysis found no actual side effects in its body. The hook does not perform I/O, modify external state, or call other impure code. Marking a side-effect-free hook as impure is misleading — callers cannot benefit from purity optimizations, and the annotation does not match the actual behavior.

This is only reported when the hook cannot be overridden — either the declaring class is final, or the hook itself is declared final. For hooks that a subclass could override with a side-effecting implementation, PHPStan does not report this.

How to fix it #

Remove the @phpstan-impure annotation since the hook has no side effects:

 public int $value {
-	/** @phpstan-impure */
 	get => $this->backing;
 }

If the hook is supposed to have side effects, add them (and keep the annotation). If it is genuinely pure, you may mark it accordingly:

 public int $value {
-	/** @phpstan-impure */
+	/** @phpstan-pure */
 	get => $this->backing;
 }

How to ignore this error #

You can use the identifier impurePropertyHook.pure to ignore this error using a comment:

// @phpstan-ignore impurePropertyHook.pure
codeThatProducesTheError();

You can also use only the identifier key to ignore all errors of the same type in your configuration file in the ignoreErrors parameter:

parameters:
	ignoreErrors:
		-
			identifier: impurePropertyHook.pure

Rules that report this error #

• PHPStan\Rules\Pure\PureFunctionRule [1]
• PHPStan\Rules\Pure\PureMethodRule [1]
• PHPStan\Rules\Pure\PurePropertyHookRule [1]