对ecshop无限级分类的解析

对ecshop无限级分类的解析,认真分析后发现真的其算法还是比较精典的其实并不难理解，有举例方便大家理解function cat_options($spec_cat_id, $arr)
{
    static $cat_options = array();    if (isset($cat_options[$spec_cat_id]))
    {
        return $cat_options[$spec_cat_id];
    }
      /*
        初始化关键参数:
        $level:当前子节点深度
        $last_cat_id:当前父节点ID
        $options:带有缩进级别的数组
        $cat_id_array:沿同一路径的父节点依次进驻
        $level_array:该节点的子节点深度,也是依次进驻
       */    if (!isset($cat_options[0]))
    {
        $level = $last_cat_id = 0;
        $options = $cat_id_array = $level_array = array();
        while (!empty($arr))//如果还有待构造的节点则继续遍历
        { 
            foreach ($arr AS $key => $value)
            {   
                $cat_id = $value['cat_id'];
                //一级分类结点
                if ($level == 0 && $last_cat_id == 0)
                {   
                    if ($value['parent_id'] > 0)
                    {
                        break;
                    }
                    $options[$cat_id]          = $value;
                    $options[$cat_id]['level'] = $level;
                    $options[$cat_id]['id']    = $cat_id;
                    $options[$cat_id]['name'] = $value['cat_name'];
                    //遍历过了就不再遍历
                    unset($arr[$key]);
                    if ($value['has_children'] == 0)
                    {
                        continue;
                    }
                    $last_cat_id = $cat_id;//下层结点的父亲结点
                    $cat_id_array = array($cat_id);
                    $level_array[$last_cat_id] = ++$level;
                    continue;
                }
     //当前结点的父亲结点ID等于它的上一级结点ID
                if ($value['parent_id'] == $last_cat_id)
                {   
                    $options[$cat_id]          = $value;
                    $options[$cat_id]['level'] = $level;
                    $options[$cat_id]['id']    = $cat_id;
                    $options[$cat_id]['name'] = $value['cat_name'];
                    unset($arr[$key]);//遍历过了就不再遍历
                    //如果当前结点有孩子则当前结点要进驻,但不再遍历;反之不进驻也不再遍历
                    if ($value['has_children'] > 0)
                    {
                        if (end($cat_id_array) != $last_cat_id)
                        {
                            $cat_id_array[] = $last_cat_id;
                        }
                        $last_cat_id    = $cat_id;//当现结点做为下一级结点的新的父亲结点
                        $cat_id_array[] = $cat_id;//进驻
                       
                    $level_array[$last_cat_id] = ++$level;//当前结点的下一级结点深度
                    }
                   
                }
                elseif ($value['parent_id'] > $last_cat_id)
                {//如果当前结点父亲深度大于目前父亲结点的深度则进行下一轮循环
                    break;
                }
            }//endforeach
            $count = count($cat_id_array);
            if ($count > 1)
            {
               //取出最后进驻的父亲节点作为当前父亲节点
                $last_cat_id = array_pop($cat_id_array);
            }
            elseif ($count == 1)
            {
                if ($last_cat_id != end($cat_id_array))
                {
                //进驻的父亲结点只有一个时并且没有作为当前父亲节点时把它取出
                    $last_cat_id = end($cat_id_array);
                }
                else
                {   //否则最后取出的父亲结点一定是一级分类结点
                    $level = 0;
                    $last_cat_id = 0;
                    $cat_id_array = array();
                    continue;
                }
            }
           
            if ($last_cat_id && isset($level_array[$last_cat_id]))
            { 
               //取出当前结点的深度
                $level = $level_array[$last_cat_id];
            }
            else
            { 
                $level = 0;
            }
        }//end while,此时已完成非递归前序遍历构造树的工作,其中$options已保存了从根结点开始的所有结点带有分层性质的数组
        $cat_options[0] = $options;
    }
    else
    {
        $options = $cat_options[0];
    }
    //如果从0开始即取整个树则直接返回不再处理.
    if (!$spec_cat_id)
    {
        return $options;
    }
    //否则开始从指定结点截取,以下比较简单我还是稍微说说吧,要说就说几个参数含义吧
    /*
    $spec_cat_id_level:截取结点的深度
    $spec_cat_id_array:最终返回的以该结点为根结点的一棵商品分类树
    最终返回的数组是这样排序的:按父亲结点大小,按直接父亲结点,按同一父亲结点这样的先根遍历,具个例子:
    一级结点有1,5 二级结点有2,6,7 三级结点有8,9,如果1的直接孩子是2,6而2的直接孩子是8,9;另外
    5的直接孩子是7那么最终的数组是这样排列的1->2->8->9->6->5->7 
    */
    else
    {
        if (empty($options[$spec_cat_id]))
        {
            return array();
        }        $spec_cat_id_level = $options[$spec_cat_id]['level'];
    
        foreach ($options AS $key => $value)
        {
            if ($key != $spec_cat_id)
            {
                unset($options[$key]);
            }
            else
            {
                break;
            }
        }        $spec_cat_id_array = array();
        foreach ($options AS $key => $value)
        {
            if (($spec_cat_id_level == $value['level'] && $value['cat_id'] != $spec_cat_id) ||
                ($spec_cat_id_level > $value['level']))
            {
                break;
            }
            else
            {
                $spec_cat_id_array[$key] = $value;
            }
        }
        $cat_options[$spec_cat_id] = $spec_cat_id_array;
        return $spec_cat_id_array;
    }
}