步驟1.

php artisan make:controller Api\\HwController

步驟2.

//app\\Http\\Controllers\\Api\\HwController.php

namespace App\\Http\\Controllers\\Api;

use App\\Http\\Controllers\\Controller;
use Illuminate\\Http\\Request;

class HwController extends Controller
{
    public function times(Request $request)
    {
        $status = 0;
        if (!$request->has('x') || !$request->has('y')) {
            $message = 'x 或 y 不存在';
        } else {
            $x = $request->x;
            $y = $request->y;
            if (!is_numeric($x) || !is_numeric($y)) {
                $message = 'x 或 y 不是數字';
            } else {
                $result = $x * $y;
                $status = 1;
            }
        }
        if ($status == 1) {
            return ['status' => $status, 'result' => $result];
        } else {
            return ['status' => $status, 'message' => $message];
        }
    }
}

步驟3.

//routes\\api.php

Route::post('/hw/times', 'App\\Http\\Controllers\\Api\\HwController@times');