syntax error unexpected $i (T_VARIABLE) expecting in Laravel 8.0

This is my first task in PHP with Laravel 8.0 framework. Although Laravel has made the development very smooth as compare to conventional PHP we used quite a few years back. But I miss the open flair of conventional PHP. It was too simple there to generate and access pages by creating customized URLs during the runtime itself. In laravel I am trying to re-engineer my conventional PHP code, but unable to map to the customized URL. Some assistance required for the code snipped shared herewith:

public function updateMethod(Request $request)
    {
       $i = 1;
       dd($request->input_name_$i);
    }

When I execute this function in conventional PHP it runs fine. but with Laravel 8.0, it generates error as

syntax error, unexpected '$i' (T_VARIABLE), expecting ')'

However, if I change it as below, it runs fine

public function updateMethod(Request $request)
{
   $i = 1;
   dd($request->input_name_1);
}

But I need this to be dynamically updated at the runtime.