一、陣列

$categories = array(
    array('id'=>1,'name'=>'陝西','parent_id'=>0),
    array('id'=>2,'name'=>'西安','parent_id'=>1),
    array('id'=>3,'name'=>'長安區','parent_id'=>2),
    array('id'=>4,'name'=>'河南','parent_id'=>0),
    array('id'=>5,'name'=>'鄭州','parent_id'=>4),
    array
 
('id'=>6,'name'=>'河北','parent_id'=>0),
    array('id'=>7,'name'=>'石家莊','parent_id'=>6),
    array('id'=>8,'name'=>'新華區','parent_id'=>7))；

二、非遞迴實現無限極分類

    function getTree($categories)
    {
        //第一步，將分類id作為陣列key,並建立node單元
        $tree = array();
        foreach($categories as $category){
            $tree[$category['id']] = $category;
            $tree[$category['id']]['node'] = array();
        }
        //第二步，利用引用，將每個分類新增到父類node陣列中，這樣一次遍歷即可形成樹形結構。
        foreach($tree as $key=>$item){
            if($item['parent_id'] != 0){
                $tree[$item['parent_id']]['node'][] = &$tree[$key];//注意：此處必須傳引用否則結果不對
                if($tree[$key]['node'] == null){
                    unset($tree[$key]['node']); //如果node為空，則刪除該node元素
                }
            }
        }
        //第三步，刪除無用的非根節點資料
        foreach($tree as $key=>$category){
            if($category['parent_id'] != 0){
                unset($tree[$key]);
            }
        }
        return $tree;
    }　

三、效果

Array
(
    [1] => Array
        (
            [id] => 1
            [name] => 陝西
            [parent_id] => 0
            [node] => Array
                (
                    [0] => Array
                        (
                            [id] => 2
                            [name] => 西安
                            [parent_id] => 1
                            [node] => Array
                                (
                                    [0] => Array
                                        (
                                            [id] => 3
                                            [name] => 長安區
                                            [parent_id] => 2
                                        )

                                )

                        )

                )

        )

    [4] => Array
        (
            [id] => 4
            [name] => 河南
            [parent_id] => 0
            [node] => Array
                (
                    [0] => Array
                        (
                            [id] => 5
                            [name] => 鄭州
                            [parent_id] => 4
                        )

                )

        )

    [6] => Array
        (
            [id] => 6
            [name] => 河北
            [parent_id] => 0
            [node] => Array
                (
                    [0] => Array
                        (
                            [id] => 7
                            [name] => 石家莊
                            [parent_id] => 6
                            [node] => Array
                                (
                                    [0] => Array
                                        (
                                            [id] => 8
                                            [name] => 新華區
                                            [parent_id] => 7
                                        )

                                )

                        )

                )

        )

)