保存另一个函数的值并检查PHP

我再次调用THIS函数，所以我得到了一些新的$key is THIS，我想把它添加到同一个数组中，这样我就可以检查它是否相同，是否唯一。比如全局数组。

function getNodesInfo($node)
    {
               foreach ($result as  $key => $value)
                        {   
                          $items[]=$key;
                        }
                        echo ("-----."'n"); 
                        print_r($items."'n");
    getNodesInfo($subNode);
    }

这是我的输出

-------
Array
(
    [0] => author
    [1] => title
    [2] => genre
    [3] => price
    [4] => publish_date
    [5] => description
)
-------
Array
(
    [0] => author
    [1] => title
    [2] => genre
    [3] => price
    [4] => publish_date
    [5] => description
)
-------
Array
(
    [0] => book
)

我希望我的输出看起来像

Array
(
    [0] => author
    [1] => title
    [2] => genre
    [3] => price
    [4] => publish_date
    [5] => description
)
-------
Array
(
    [0] => book
)