Bug report

If array is used as foreach key, phpstan reports $context["_key"] as non existing offset, but it is defined (tested on PHP 8.1).

Also related: Offset can exist (if $context["value"] is not empty) outside of forech scope, so calling unset should be safe.

Code snippet that reproduces the problem

<?php declare(strict_types = 1);

$context = [
    'values' => [1, 2, 3],
];
foreach ($context['values'] as $context["_key"] => $context["value"]) {
    echo sprintf("Key: %s, Value: %s\n", $context["_key"], $context["value"]);
}

unset($context["_key"]);

https://phpstan.org/r/6a63cb67-ecf7-484b-87b3-283595ddd3ef

Expected output

No errors

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