yii\db\ActiveQuery::removeDuplicatedModels PHP Method

    private function removeDuplicatedModels($models)
    {
        $hash = [];
        /* @var $class ActiveRecord */
        $class = $this->modelClass;
        $pks = $class::primaryKey();
        if (count($pks) > 1) {
            // composite primary key
            foreach ($models as $i => $model) {
                $key = [];
                foreach ($pks as $pk) {
                    if (!isset($model[$pk])) {
                        // do not continue if the primary key is not part of the result set
                        break 2;
                    }
                    $key[] = $model[$pk];
                }
                $key = serialize($key);
                if (isset($hash[$key])) {
                    unset($models[$i]);
                } else {
                    $hash[$key] = true;
                }
            }
        } elseif (empty($pks)) {
            throw new InvalidConfigException("Primary key of '{$class}' can not be empty.");
        } else {
            // single column primary key
            $pk = reset($pks);
            foreach ($models as $i => $model) {
                if (!isset($model[$pk])) {
                    // do not continue if the primary key is not part of the result set
                    break;
                }
                $key = $model[$pk];
                if (isset($hash[$key])) {
                    unset($models[$i]);
                } elseif ($key !== null) {
                    $hash[$key] = true;
                }
            }
        }
        return array_values($models);
    }