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<?php $levels = [1=>10, 2=>20, 3=>30, 6=>60]; $a = array_keys($levels); sort($a); $max = end($a); $toAdd = array_diff(array_keys(array_fill(1, $max, 0)), $a); $result = array_fill_keys($toAdd, 0); $merged = array_merge($levels, $result); var_dump($result); var_dump($merged);

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