php generate json tree from array

php generate json tree from array

function genTree($items, $idkey='_id'){
    $tree = array();
    foreach($items as $item){
        if(isset($items[$item['pid']])){
            $items[$item['pid']]['son'][] = &$items[$item[$idkey]];
        }else{
            $tree[] = &$items[$item[$idkey]];
        }
    }
    return $tree;
}