Error Identifier: arrayFilter.empty

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 array{} $empty */
$empty = [];

array_filter($empty);

Why is it reported? #

Calling array_filter() without a callback on an empty array has no effect. The array is already empty, so there are no elements to filter. This is likely a sign that the variable is not populated as intended, or the array_filter() call is unnecessary.

How to fix it #

Remove the unnecessary array_filter() call if the array is intentionally empty:

 <?php declare(strict_types = 1);
 
-$result = array_filter([]);
+$result = [];

Or ensure the array is populated before filtering:

 <?php declare(strict_types = 1);
 
-/** @var array{} $items */
-$items = [];
+/** @var array<int, string|null> $items */
+$items = getItems();

 array_filter($items);

How to ignore this error #

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

// @phpstan-ignore arrayFilter.empty
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.empty

Rules that report this error #

PHPStan\Rules\Functions\ArrayFilterRule [1]

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