作者寄语：
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function to_tree($items) {
foreach ($items as $item)
$items[$item['pid']]['_child'][$item['id']] = &$items[$item['id']];
return isset($items[0]['_child']) ? $items[0]['_child'] : array();
}
//注意key自增
function to_tree2($items) {
$tree = array();
foreach ($items as $item)
if (isset($items[$item['pid']]))
$items[$item['pid']]['_child'][] = &$items[$item['id']];
else
$tree[] = &$items[$item['id']];
return $tree;
} 
payonesmile
积分：2801
等级：LV3