从多维数组中获取最后6个值

function getLastSixElements($array) {
    $result = [];
    $flattened = iterator_to_array(new RecursiveIteratorIterator(new RecursiveArrayIterator($array)), false);
    $lastSix = array_slice($flattened, -6);
    foreach ($lastSix as $value) {
        $result[] = $value;
    }
    return $result;
}

$multiDimensionalArray = [
    [1, 2, 3],
    [4, 5, 6],
    [7, 8, 9],
    [10, 11, 12],
    [13, 14, 15],
    [16, 17, 18],
    [19, 20, 21],
];

$lastSixElements = getLastSixElements($multiDimensionalArray);
print_r($lastSixElements);