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<?php $one = [1]; $two = [42]; $arr1 = ['k' => &$one]; $arr2 = ['k' => &$two]; var_dump(current($arr1['k']), current($arr2['k'])); array_replace_recursive($arr1, $arr2); var_dump(current($arr1['k']), current($arr2['k']));

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57.72 ms | 402 KiB | 5 Q