将具有n个项目的1维数组转换为n维数组

How to convert this:

$arr = array('item1','item2','item3','item4','...');

to this:

$arr2['item1']['item2']['item3']['item4']['...'] = $something;

$arr2 = $something;
foreach (array_reverse($arr) as $key) {
    $arr2 = array($key => $arr2);
}