How get all subcategories of specific category?

Question

I have a file left.phtml for a vertical menu. I want to get all subcategories of specific category ID3. I have this code.

<?php if (!Mage::registry('current_category')) return ?>
<?php
$categoryId = 3;
$category = Mage::getModel('catalog/category')->load($categoryId);
$_categories = $category->getChildrenCategories();
?>
<?php $_count = is_array($_categories)?count($_categories):$_categories->count(); ?>
<?php if($_count): ?>
<div class="block block-layered-nav block-layered-nav--no-filters">
    <div class="block-content toggle-content open">
        <dl id="narrow-by-list2">
            <dt><?php echo $this->__('Каталог') ?></dt>
            <dd>
                <ol>
                <?php foreach ($_categories as $_category): ?>
                    <?php if($_category->getIsActive()): ?>
                    <li>
                        <a href="<?php echo $this->getCategoryUrl($_category) ?>"<?php if ($this->isCategoryActive($_category)): ?> class="current"<?php endif; ?>>
                            <?php echo $this->escapeHtml($_category->getName()) ?>
                        </a>
                    </li>
                    <?php endif; ?>
                <?php endforeach ?>
                </ol>
            </dd>
        </dl>
        <script type="text/javascript">decorateDataList('narrow-by-list2')</script>
    </div>
</div>
<?php endif; ?>

Example:

Category ID 3 (level 0)
  Category (level 1)
    Subcategory (level 2)
      Subcategory (level 3)
    Subcategory
      Subcategory (level 3)
    Subcategory
      Subcategory (level 3)
  Category (level 1) 
    Subcategory 
    Subcategory
    Subcategory
  Category (level 1) 
    Subcategory
    Subcategory
    Subcategory

Answer 1

Try this::

<?php $_helper = Mage::helper('catalog/category') ?>
<?php $categoryId = 3;?>
<?php $category = Mage::getModel('catalog/category')->load($categoryId) ?>
<?php $_categories = $category->getChildrenCategories() ?>

<?php if (count($_categories) > 0): ?>
    <ul>
        <?php foreach($_categories as $_category): ?>
            <li>
                <a href="<?php echo $_helper->getCategoryUrl($_category) ?>"><?php echo $_category->getName() ?></a>
                <?php $_category = Mage::getModel('catalog/category')->load($_category->getId()) ?>
                <?php if($_category->hasChildren()):?>
                <?php $_subcategories = $_category->getChildrenCategories() ?>
                    <ul>
                        <?php foreach($_subcategories as $_subcategory): ?>
                            <li>
                                <a href="<?php echo $_helper->getCategoryUrl($_subcategory) ?>"><?php echo $_subcategory->getName() ?></a>
                                <?php $_category2 = Mage::getModel('catalog/category')->load($_subcategory->getId()) ?>
                                <?php if($_category2->hasChildren()):?>
                                <?php $_subcategories2 = $_category2->getChildrenCategories() ?>
                                    <ul>
                                        <?php foreach($_subcategories2 as $_subcategory2): ?>
                                            <li>
                                                <a href="<?php echo $_helper->getCategoryUrl($_subcategory2) ?>"><?php echo $_subcategory2->getName() ?></a>
                                            </li>
                                        <?php endforeach; ?>
                                    </ul>
                                <?php endif; ?>

                            </li>
                        <?php endforeach; ?>
                    </ul>
                <?php endif; ?>
            </li>
        <?php endforeach; ?>
    </ul>
<?php endif; ?>

Answer 2

Here is code you can use:

$children = Mage::getModel('catalog/category')->getCategories(3);
foreach ($children as $category) {
      echo $category->getName();
}

Thanks to @clockworkgeek for the answer

Answer 3

To get a collection of subcategories, with their subcategories, and so on, of a given category $parentCategory, you can use:

$subcategoryCollection = Mage::getModel('catalog/category')
    ->getCollection()
    ->addFieldToFilter('path', ['like' => $parentCategory->getData('path') . '/%']);

(as described here: https://stackoverflow.com/q/5564647/664108)

This is a single collection load, so there is no need for additional load() methods on the category model, as in the recursive solutions.

But since you want to output the categories as tree, you can also use the category tree model, which uses the same method internally:

$categoryTree = Mage::getResourceModel('catalog/category')->getCategories(3, 0, true);

The parameters are:

• category_id
• recursion_level (0 for no limit)
• sorted

$categoryTree is now a Varien_Data_Tree_Node_Collection instance that contains all category data in tree form. Use it as follows:

<?php foreach ($categoryTree as $_category): ?>
    <?php if($_category->getIsActive()): ?>
    <li>
        <a href="<?php echo $this->getCategoryUrl($_category) ?>"<?php if ($this->isCategoryActive($_category)): ?> class="current"<?php endif; ?>>
            <?php echo $this->escapeHtml($_category->getName()) ?>
        </a>

        <?php foreach ($_category->getChildren() as $_subCategory): ?>

            // repeat for second level, or create a function and use recursion for arbitrary deep nesting

        <?php endforeach; ?>
    </li>
    <?php endif; ?>
<?php endforeach ?>

$_category is a Varien_Data_Tree_Node instance, so getChildren() is not the same method as the one in the category model and it does not have all the other methods, but it's a Varien_Object that contains the category data, so all the magic getters work.

---

Summary

Here is a complete code example with recursive function, that you can copy and paste into your template and modify as needed (the function needs at least PHP 5.4 to work, I hope that's not a problem):

<?php
$categoryId = 3;
$categoryTree = Mage::getResourceModel('catalog/category')->getCategories($categoryId, 0, true);
$printCategories = function($nodes) use (&$printCategories) {
    ?><ol>
    <?php foreach ($nodes as $_category): ?>
        <?php if($_category->getIsActive()): ?>
        <li>
            <a href="<?php echo $this->getCategoryUrl($_category) ?>"<?php if ($this->isCategoryActive($_category)): ?> class="current"<?php endif; ?>>
                <?php echo $this->escapeHtml($_category->getName()) ?>
            </a>

            <?php $printCategories($_category->getChildren()); ?>

        </li>
        <?php endif; ?>
    <?php endforeach; ?>
    </ol>
    <?php
};
$printCategories($categoryTree);
?>

Answer 4

This is another way to get child category using Category Tree:

public function getCategoryTree()
{
    $model = Mage::getModel('catalog/category_api');
    $treeData = $model->tree();
    return $this->_sendJsonRespond('success', $treeData, null, null);
}

Hope this may work for you.