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Error Identifier: arrayFilter.same

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);

/** @var list<positive-int> $numbers */
$numbers = [1, 2, 3];

$filtered = array_filter($numbers);

Why is it reported? #

When array_filter() is called without a callback, PHP removes all falsy values from the array. PHPStan has determined that the array’s value type does not contain any falsy values (such as 0, '', null, false, or []), so the call has no effect – the array will always stay the same after filtering.

In the example above, the array contains only positive integers, which are always truthy, so array_filter() cannot remove any elements.

How to fix it #

If the filtering is unnecessary, remove the array_filter() call:

 <?php declare(strict_types = 1);
 
 /** @var list<positive-int> $numbers */
 $numbers = [1, 2, 3];

-$filtered = array_filter($numbers);
+$filtered = $numbers;

If you intended to filter by a specific condition, provide an explicit callback:

 <?php declare(strict_types = 1);
 
 /** @var list<positive-int> $numbers */
 $numbers = [1, 2, 3];

-$filtered = array_filter($numbers);
+$filtered = array_filter($numbers, static function (int $value): bool {
+    return $value > 1;
+});

How to ignore this error #

You can use the identifier arrayFilter.same to ignore this error using a comment:

// @phpstan-ignore arrayFilter.same
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: arrayFilter.same

Rules that report this error #

• PHPStan\Rules\Functions\ArrayFilterRule [1]

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