The Below code is tell you how to check a category exist in magento and this function will create Parent and sub category automatically in magento.

This function is first check category exist or not . if category does not exit than create a new category and return it’s category Id.

$cat_name = 'new category';
$p_cat_id = $this->createParentCategory($cat_name);

This function is first check child category exit on parent category or not. . if category does not exit than create a new category and return it’s category Id.

$child_cat_name = 'new child category';
$c_cat_id = $this->createParentCategory($child_cat_name,$p_cat_id);

protected function createParentCategory($cat_name,$parentId) {
           
            $categories = Mage::getResourceModel('catalog/category_collection');
            $categories->addAttributeToFilter('is_active', 1)
                ->addAttributeToFilter('name', $cat_name)
                ->setCurPage(1)->setPageSize(1)
                ->load();
            
            $pId = $categories->getData();
            $pId = $pId[0]['entity_id'];
            if ($pId)  {
               $pId = $pId;           
            }else {
                    $parentId = $parentId?$parentId:'2';
                    $category = new Mage_Catalog_Model_Category();
                    $category->setName($cat_name);
                    //$category->setUrlKey('new-category');
                    $category->setIsActive(1);
                    $category->setDisplayMode('PRODUCTS');
                    $category->setIsAnchor(0);

                    $parentCategory = Mage::getModel('catalog/category')->load($parentId);
                    $category->setPath($parentCategory->getPath());
                    $category->save(); 
                    unset($category);
                    $pId = $this->getCategoryId($cat_name);
             }
            return $pId;
        }

 protected function getCategoryId($cat_name) {
           
            $categories = Mage::getResourceModel('catalog/category_collection');
            $categories->addAttributeToFilter('is_active', 1)
                ->addAttributeToFilter('name', $cat_name)
                ->setCurPage(1)->setPageSize(1)
                ->load();
            $pId = $categories->getData();        
          return  $pId[0]['entity_id'];
        }

If you want delete all category in magento Click Here
If you want delete all Product in magento Click Here

by