how to convert javascript btoa(string) to laravel http client format?

hello

I tried to convert curl request to laravel 10 http client format.

 curl -X POST -d "grant_type=client_credentials" -d "scope=connect.api.read connect.api.write" 
  -u "{client_id}:{client_secret}"
  https://api.connect.domain.com/as/token.oauth2 

to 		

 $basic_data = config('services.elements.clientID'). ':' . config('services.elements.secretID');


    $basic = base64_encode($basic_data);
    $response = Http::
    withHeaders([
       'Authorization' => 'Basic ' .$basic,
       'content-type'=> 'application/x-www-form-urlencoded'
     ])
    ->post('https://api.connect.domain.com/as/token.oauth2',[
        'grant_type'=>'client_credentials',
        'scope'=>'connect.api.read'
    ]);


    dd($response);

-- Api documentation gives example in Javascript:

 const client = '...' // client id;
 const secret = '...' // secret value
const basic = btoa(`${client}:${secret}`);
const opts = {
  headers: {
   'Authorization': `Basic ${basic}`,
   'user-agent': 'NodeJs',
   'Content-type': 'application/x-www-form-urlencoded'
   },
  method: 'POST'
 };

Question: javascript

   const basic = btoa(`${client}:${secret}`); is it same as 

   $basic_data = config('services.elements.clientID'). ':' . config('services.elements.secretID');
    $basic = base64_encode($basic_data);   ??

--> Api gives me error " 400" ?

     reasonPhrase: "Bad Request"
    -statusCode: 400.

Thanks Mika.