argument.bitmaskNotAllowed

Code example

<?php declare(strict_types = 1);

$a = [3, 1, 2];
$unique = array_unique($a, SORT_REGULAR | SORT_NUMERIC);

Why is it reported?

The $flags parameter of array_unique() accepts a single sorting constant, not a bitmask of combined constants. Combining SORT_REGULAR | SORT_NUMERIC with the | operator produces an integer value that does not correspond to any valid flag, leading to unexpected behavior.

Some PHP functions accept bitmask parameters where multiple flags can be combined (like json_encode()), while others expect exactly one constant value. PHPStan knows which parameters allow bitmasks and which do not.

This check is only performed on PHP 8.0+.

How to fix it

Pass a single constant without combining:

 $a = [3, 1, 2];
-$unique = array_unique($a, SORT_REGULAR | SORT_NUMERIC);
+$unique = array_unique($a, SORT_NUMERIC);