Error Identifier: arrayFilter.alwaysEmpty

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);

$values = [null, 0];

$filtered = array_filter($values);

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 contains only falsy values (such as 0, '', null, false, or []), so the result will always be an empty array.

In the example above, the array contains null and 0, both of which are falsy, so array_filter() will always remove all elements.

How to fix it #

If the filtering is intentional, consider replacing the call with an empty array directly:

 <?php declare(strict_types = 1);
 
 $values = [null, 0];

-$filtered = array_filter($values);
+$filtered = [];

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

 <?php declare(strict_types = 1);
 
 $values = [null, 0];

-$filtered = array_filter($values);
+$filtered = array_filter($values, static function ($value): bool {
+    return $value !== null;
+});

If the array is expected to contain non-falsy values, fix the type of the source data:

 <?php declare(strict_types = 1);
 
-$values = [null, 0];
+$values = [1, 2, 3];

 $filtered = array_filter($values);

How to ignore this error #

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

// @phpstan-ignore arrayFilter.alwaysEmpty
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.alwaysEmpty

Rules that report this error #

PHPStan\Rules\Functions\ArrayFilterRule [1]

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