Display top level categories & sub categories from template files - Magento 1

<?php $_helper = Mage::helper('catalog/category') ?>
<?php $_categories = $_helper->getStoreCategories() ?>
<?php $currentCategory = Mage::registry('current_category') ?>
<?php if (count($_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 $_subcategories = $_category->getChildrenCategories() ?>
				<?php if (count($_subcategories) > 0): ?>
					<ul>
						<?php foreach($_subcategories as $_subcategory): ?>
							<li>
								<a href="<?php echo $_helper->getCategoryUrl($_subcategory) ?>">
									<?php echo $_subcategory->getName() ?>
								</a>
							</li>
						<?php endforeach; ?>
					</ul>
				<?php endif; ?>
			</li>
		<?php endforeach; ?>
	</ul>
<?php endif; ?>