ThinkPHP learning (4) Multiple nested loops for advanced applications of volist tags

Action code:

 public function index(){
 $prod = I("get.prod_en");
 $id = I("get.id", 0, "int");
 if ($prod == ""){
 $serviceProduct = array();//Array traversed by multiple loops

//The data is saved in two tables, here $serviceProduct is initialized through the loop Array
 $service = M("product_class")->order("oid ASC")->select();
 for ($i = 0; $i < count($service); $i++)
 {
 array_push($serviceProduct, array("srvName"=>$service[$i]["pc_cn"], "product"=>M("product")->where("prod_class_id=".$ service[$i]["pcid"])->order("oid ASC")->select()));
 }

//If you want to use it in the template To output variables, the variables must be passed to the template in the controller. The system provides the assign method to assign values ​​to template variables. Regardless of the variable type, assign assignment is used uniformly.
 $this->assign("serviceProduct", $serviceProduct);
 $this->display();
 }else{
 if ($id > 0){
 $this->display("detail ");
 }else{
 $this->assign('prod_en', $prod);
 $clsList = M("question_class")->order("oid ASC")->select();
 $this->assign('clsList', $clsList);

 $qusList = M("question")->order("oid ASC")->select();
 $this-> assign('qusList', $qusList);
 $this->display("list");
 }
 }
 }

2. {$sp.srvName}
4. {$pd.prod_cn}
6. |
13. Specify the key value and use