callable.void

Code example

<?php declare(strict_types = 1);

/** @var callable(): void $callback */
$callback = static function (): void {};

$result = $callback();

Why is it reported?

The result of calling a callable that returns void is being used. A void return type indicates that the function or callable does not return a meaningful value. Using the result of such a call is a logic error because the value is always null and the function author has explicitly declared no value should be expected.

In the example above, $callback is typed as callable(): void, so assigning $callback() to $result is using a void return value.

How to fix it

Do not use the return value of a void callable. Call it as a standalone statement instead:

 <?php declare(strict_types = 1);

 /** @var callable(): void $callback */
 $callback = static function (): void {};

-$result = $callback();
+$callback();

If you need the callable to return a value, change its type signature to reflect the actual return type.