form validation is_unique using array

@includebeer Looks ugly.

PHP Code:

//with model 
$model = new Model();
// array or null
$notUniqueValues = $model->whereIn('field', $arrayOfValues)->groupBy('field')->findColumn('field');

//without model 
$result = db_connect()->table('table')->select('field')->whereIn('field', $arrayOfValues)->groupBy('field')->get()->getResultArray();
$notUniqueValues = $result ? array_column($result, 'field') : null;