解释下这段代码，并为每一句代码写上注释。解释每一个方法或调用的作用。// HandleController.phpnamespace app\index\controller;use think\Controller;use app\index\model\Apply;use app\index\model\ApplyNode;class HandleController extends Controller{ // 处理待办审批 public function handle() { $user_id = session('user_id'); $applyNodes = ApplyNode::where(['user_id' => $user_id, 'status' => 0])->select(); if ($this->request->isPost()) { $apply_node_id = $this->request->param('apply_node_id'); $status = $this->request->param('status'); $applyNode = ApplyNode::get($apply_node_id); $applyNode->status = $status; $applyNode->save(); $apply = $applyNode->apply; $processNodes = $apply->process->process_nodes; // 更新下一个待处理节点的user_id foreach ($processNodes as $key => $node) { if ($node->id == $applyNode->node_id) { if ($key < count($processNodes) - 1) { $nextNode = $processNodes[$key + 1]; $applyNodes = ApplyNode::where(['apply_id' => $apply->id, 'node_id' => $nextNode->id])->select(); foreach ($applyNodes as $applyNode) { $applyNode->user_id = $nextNode->role->getUserId(); $applyNode->status = 0; $applyNode->save(); } } else { $apply->status = 1; $apply->save(); } break; } } $this->success('处理成功'); } else { $this->assign('applyNodes', $applyNodes); return $this->fetch(); } }}

这段代码是一个用于处理待办审批的控制器代码，下面是注释：

// 指定命名空间
namespace app\index\controller;
// 引入Controller类
use think\Controller;
// 引入Apply、ApplyNode模型
use app\index\model\Apply;
use app\index\model\ApplyNode;

// 定义HandleController控制器类，继承自Controller类
class HandleController extends Controller{
    // 处理待办审批
    public function handle()
    {
        // 获取当前用户的user_id
        $user_id = session('user_id');
        // 获取未处理的申请节点
        $applyNodes = ApplyNode::where(['user_id' => $user_id, 'status' => 0])->select();
        // 如果是POST请求，更新节点状态并进行下一步处理
        if ($this->request->isPost()) {
            // 获取传递过来的参数
            $apply_node_id = $this->request->param('apply_node_id');
            $status = $this->request->param('status');
            // 获取申请节点
            $applyNode = ApplyNode::get($apply_node_id);
            // 更新节点状态
            $applyNode->status = $status;
            $applyNode->save();
            // 获取申请对象
            $apply = $applyNode->apply;
            // 获取流程节点列表
            $processNodes = $apply->process->process_nodes;
            // 更新下一个待处理节点的user_id
            foreach ($processNodes as $key => $node) {
                if ($node->id == $applyNode->node_id) {
                    if ($key < count($processNodes) - 1) {
                        $nextNode = $processNodes[$key + 1];
                        $applyNodes = ApplyNode::where(['apply_id' => $apply->id, 'node_id' => $nextNode->id])->select();
                        foreach ($applyNodes as $applyNode) {
                            $applyNode->user_id = $nextNode->role->getUserId();
                            $applyNode->status = 0;
                            $applyNode->save();
                        }
                    } else {
                        $apply->status = 1;
                        $apply->save();
                    }
                    break;
                }
            }
            // 处理成功，返回提示信息
            $this->success('处理成功');
        } else {
            // 如果不是POST请求，返回视图，并分配申请节点数据
            $this->assign('applyNodes', $applyNodes);
            return $this->fetch();
        }
    }
}

注释中解释了每一句代码的作用，包括定义命名空间、引入模型、定义控制器类、处理待办审批、获取用户ID、获取未处理的申请节点、更新节点状态、获取申请对象、获取流程节点列表、更新下一个待处理节点的user_id等。