Error Identifier: arrayFilter.strict
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<int> $list */
$list = [1, 2, 3];
// No callback provided - uses loose comparison
array_filter($list);
Why is it reported? #
When array_filter() is called without a callback (parameter #2), PHP uses loose comparison to determine which elements to keep. Each value is cast to bool using PHP’s type juggling rules, which means values like 0, '', '0', null, and [] are considered falsy and are removed. This implicit behaviour can lead to unexpected results when the intent is to filter specific values.
This rule is part of phpstan-strict-rules and requires an explicit callback to make the filtering logic clear and intentional.
How to fix it #
Provide an explicit callback function that defines the filtering logic:
<?php declare(strict_types = 1);
/** @var list<int> $list */
$list = [1, 2, 3];
-array_filter($list);
+array_filter($list, static function (int $value): bool {
+ return $value > 0;
+});
If the intent is truly to remove all falsy values, make it explicit:
<?php declare(strict_types = 1);
/** @var list<int> $list */
$list = [1, 2, 3];
-array_filter($list);
+array_filter($list, static function (int $value): bool {
+ return (bool) $value;
+});
How to ignore this error #
You can use the identifier arrayFilter.strict to ignore this error using a comment:
// @phpstan-ignore arrayFilter.strict
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.strict