yii\db\ActiveRelationTrait::buildBuckets PHP Method

    private function buildBuckets($models, $link, $viaModels = null, $viaLink = null, $checkMultiple = true)
    {
        if ($viaModels !== null) {
            $map = [];
            $viaLinkKeys = array_keys($viaLink);
            $linkValues = array_values($link);
            foreach ($viaModels as $viaModel) {
                $key1 = $this->getModelKey($viaModel, $viaLinkKeys);
                $key2 = $this->getModelKey($viaModel, $linkValues);
                $map[$key2][$key1] = true;
            }
        }
        $buckets = [];
        $linkKeys = array_keys($link);
        if (isset($map)) {
            foreach ($models as $model) {
                $key = $this->getModelKey($model, $linkKeys);
                if (isset($map[$key])) {
                    foreach (array_keys($map[$key]) as $key2) {
                        $buckets[$key2][] = $model;
                    }
                }
            }
        } else {
            foreach ($models as $model) {
                $key = $this->getModelKey($model, $linkKeys);
                $buckets[$key][] = $model;
            }
        }
        if ($checkMultiple && !$this->multiple) {
            foreach ($buckets as $i => $bucket) {
                $buckets[$i] = reset($bucket);
            }
        }
        return $buckets;
    }