类stdClass的对象无法转换为字符串

public function get($id = null)
{
    $terms                  = array('id' => $id);
    $blog                   = $this->model->getBy($terms); 

    // $blog => (object) [id => 1, category_id => 3]

    $fix->id                = $blog->id;
    // $fix->category       = $this->getCategory($blog->category_id); // Not work
    $fix->cat_or_something = $this->getCategory($blog->category_id); // Work

    return $fix;

    // $fix => (object) [id => 1, cat_or_something => [name => Some Category]]
}

如果我把$fix->category换成$fix->cat_or_something，就可以了。$fix->category有点奇怪。