src/TaggableBehavior.php
public function getTagValues($asString = false)
    {
        if ($this->_tagsList === null && !$this->owner->getIsNewRecord()) {
            // the list of tags is not initialized
            $this->_tagsList = [];
            // trying to obtain related models
            $relation = $this->owner->getRelation('tagsList', false);
            if ($relation instanceof ActiveQuery) {
                $this->_tagsList = array_unique($relation->select('text')->column());
            }
        }
        return $asString === true ? implode(',', $this->_tagsList) : $this->_tagsList;
    }
public function getTagValues($asString = false)
    {
        if ($this->_tagsList === null && !$this->owner->getIsNewRecord()) {
            // the list of tags is not initialized
            $this->_tagsList = [];
            // trying to obtain related models
            $relation = $this->owner->getRelation('tagsList', false);
            if ($relation instanceof ActiveQuery) {
                $this->_tagsList = array_unique($relation->select('text')->column());
            }
        }
        return $asString === true ? implode(',', $this->_tagsList) : $this->_tagsList;
    }
Get tags list
@param bool $asString sign get a list of tags as string
@return string[]|string