gistfile1.php

public function addTag(Tag $tag)
{
    if ($this->collTags === null) {
        $this->initTags();
    }
    if (!$this->collTags->contains($tag))
    {
      // ~~~
      if ($tag->getId()) {
        $tag = TagQuery::create()->findOneById($tag->getId());
      }
      // ~~~
      $this->doAddTag($tag);

      $this->collTags[]= $tag;
    }
}