3v4l.org

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<?php $a = [7,7,7,7]; $b = [7,7,7]; $a = array_map(fn(int|array $element) => is_int($element) ? [$element] : $element, $a); $b = array_map(fn(int|array $element) => is_int($element) ? [$element] : $element, $b); $key = key(array_diff_assoc(array_merge(...$a), array_merge(...$b))); var_dump($key);

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