In this chapter I create 4 addition, subtraction, multiplication and division equations. If the route is not set, there will always be a page error, but if the routing rules are set in the route, addition, subtraction, multiplication, and division can be performed and displayed. Why is this?

This is the addition I intercepted

<?php

namespace app\index\controller;

class Demon{

public function add($n,$m){

return $n.' '.$m.'='.($n $m);

}

}

If the route is not set in route, there will always be a page error. But if I set the route

think\Route::get('add/:n/:m','index/demon/add');

, the addition can be displayed. I have repeatedly tested the path using other expressions, and there is no problem?