app\models\Contest::votesForUser PHP Method

    public function votesForUser($user = null)
    {
        if ($user === null) {
            return [];
        }
        $votes = ContestVote::where('contest_id', $this->id)->where('user_id', $user->user_id)->get();
        return $votes->map(function ($v) {
            return $v->contest_entry_id;
        })->toArray();
    }