条款错误雄辩的地方

Question

I wanna ask why I'm getting an error of

Undefined property: Illuminate\Database\Eloquent\Collection::$user_id`

Here's my code

if(!empty($parents)){
    $transactions = $this->loadupPayment
    ->select('*')
    ->where('user_id', $parents->user_id)
    ->orderby('reference_date', 'DESC')
    ->get();
}

here's the query of $parents

    $parents = false;
    if(!empty(array_filter($request->getParams())))
    {
        $parents = $this->user
        ->leftjoin('sys_user_parent', 'sys_user_parent.user_id', '=', 'sys_user.user_id')
        ->select('*')
        ->where(function($query) use ($request) {

            $first_name = $request->getParam('first_name');
            $last_name  = $request->getParam('last_name');
            $id_no = $request->getParam('parent_no');
            $child_name = $request->getParam('child_name');

            if ($first_name != '') {
                $query->where('first_name', 'LIKE', '%'. $first_name .'%');
            }

            if ($last_name != '') {
                $query->where('last_name', 'LIKE', '%'. $last_name .'%');
            }

            if ($id_no != '') {
                $query->where('identification_number', 'LIKE', '%'. $id_no .'%');
            }

        })
        ->where('user_type_id', '3')            
        ->get();