Eloquent standalone, unable to query with count and groupBy

I think you need to replace this with

Btc::raw('COUNT(*) as btc_nb')

With this

DB::raw('COUNT(*) as btc_nb')

Or maybe even like this (according to the documentation)

Btc::select(DB::raw('count(*) as btc_nb, btc_mid, btc_type'))->get();

Documentation: https://laravel.com/docs/5.6/queries#raw-expressions

Thanks for your answer; I don't have DB variable as I run eloquent as a standalone framework (Fatal error: Uncaught Error: Class 'DB' not found ...) but I did it with my own Manager instance :

$_sql2 = new Illuminate\Database\Capsule\Manager();
...
class Btc extends Illuminate\Database\Eloquent\Model {
    static function getNb(int $mid, array $btc = [], array $etat = []) {
        global $_sql2;
        $predicate = $_sql2::raw('COUNT(btc_id) as btc_nb');
        $req = Btc::select('btc_mid', 'btc_type', $predicate)->where('btc_mid', '=', $mid);
        if(!empty($btc))
            $req->whereIn('btc_id', $btc);
        if(!empty($etat))
            $req->whereIn('btc_etat', $etat);
        // indexer le resultat sur btc_type
        $result = $req->groupBy(['btc_mid', 'btc_type'])->get();
        return index_array($result, 'btc_type');
    }
}

I don't know how to do it without the 'global' variable instance of Manager() and even if it is possible? Anyway, it works as it :)

(edit) I did it by defining my own DB class as it, it was really simple !

class DB extends Illuminate\Database\Capsule\Manager{}

Your future you or fellow programmers working on the project will thank you if you get rid of the global now.

Bobby was right but you had this error; Fatal error: Uncaught Error: Class 'DB' not found because you didnt reference it by the full namespace, or including it at the top with the use statement.

If you use PHPStorm you can let it autocomplete it for you with Alt + Enter.