argument.duplicate

Code example

<?php declare(strict_types = 1);

function foo(int $a, int $b, int $c = 3, int $d = 4): int
{
	return $a + $b + $c + $d;
}

foo(...[1, 2], b: 20);

Why is it reported?

Named arguments in PHP must not overwrite a positional argument that was already passed. In the example above, the array unpacking ...[1, 2] passes values to $a and $b positionally, and then b: 20 attempts to pass $b again by name. PHP raises a fatal error at runtime in this case. This error is also reported when the same named parameter is explicitly provided more than once.

How to fix it

Remove the duplicate argument so each parameter receives exactly one value:

 <?php declare(strict_types = 1);

 function foo(int $a, int $b, int $c = 3, int $d = 4): int
 {
 	return $a + $b + $c + $d;
 }

-foo(...[1, 2], b: 20);
+foo(...[1, 2], d: 40);