Piwik\Category\Category::getId PHP Method

    public function getId()
    {
        return $this->id;
    }

 public function addCategory(Category $category)
 {
     $categoryId = $category->getId();
     if ($this->hasCategory($categoryId)) {
         throw new \Exception(sprintf('Category %s already exists', $categoryId));
     }
     $this->categories[$categoryId] = $category;
 }