arrayUnpacking.stringOffset

Code example

<?php declare(strict_types = 1);

$a = [1, 2, 3];
$b = ['key' => 'value'];

$merged = [...$a, ...$b];

Why is it reported?

Before PHP 8.1, array unpacking with the spread operator (...) only supported arrays with integer keys. Using array unpacking on an array with string keys results in a fatal error in PHP versions prior to 8.1.

In the example above, $b has the string key 'key', so unpacking it with ...$b is not supported on the configured PHP version.

How to fix it

Use array_merge() instead of array unpacking when dealing with string-keyed arrays:

 <?php declare(strict_types = 1);

 $a = [1, 2, 3];
 $b = ['key' => 'value'];

-$merged = [...$a, ...$b];
+$merged = array_merge($a, $b);

Or upgrade the project's PHP version to 8.1 or later, which supports array unpacking with string keys. Update the phpVersion setting in the PHPStan configuration accordingly.