PHP:如何通过重复值展平多维数组

function flattenArray($array) {
    $result = array();
    foreach ($array as $value) {
        if (is_array($value)) {
            $result = array_merge($result, flattenArray($value));
        } else {
            $result[] = $value;
        }
    }
    return $result;
}

$array = array(
    1,
    2,
    array(3, 4, 5),
    array(6, array(7, 8), 9),
    10
);

$flattenedArray = flattenArray($array);
print_r($flattenedArray);

Array
(
    [0] => 1
    [1] => 2
    [2] => 3
    [3] => 4
    [4] => 5
    [5] => 6
    [6] => 7
    [7] => 8
    [8] => 9
    [9] => 10
)