Get Category and subcategory ids array in Magento

Hi with the below code you will get the array of parent child categories.



$rootcatId  = Mage::app()->getStore()->getRootCategoryId();
    $root_cat   = Mage::getModel('catalog/category')->load($rootcatId);
    $categories = $this->get_child_categories($root_cat);
    echo "<pre>";
    print_r($categories);
    echo "</pre>";


    function get_child_categories($parent) {
        $cat_model = Mage::getModel('catalog/category');
        $categories = $cat_model->load($parent->getId())->getChildrenCategories();
        $ret_arr = array();
        foreach ($categories as $cat)
        {
            $ret_arr[] = array(
                                'cat_id' => $cat->getId(),
                                'cat_name' => $cat->getName(),
                                'cat_url' => $cat->getUrl(),
                                'child_cats' => $this->get_child_categories($cat),
                                );
        }
        return $ret_arr;

    }

get all categories and subcategories in magento

<?php 
$_categories = Mage::getBlockSingleton('catalog/navigation'); 
foreach ($_categories->getStoreCategories() as $_category) { 
$category = Mage::getModel('catalog/category'); 
$category->load($_category->getId()); 
$subcategories = explode(',', $category->getChildren()); 
?> 
<dl> 
<dt><?php echo $this->htmlEscape($_category->getName()); ?></dt> 
<dd> 
<ol> 
<?php 
foreach ($subcategories as $subcategoryId) { 
$category->load($subcategoryId); 
echo '<li><a href="' . $category->getURL() . '">' . $category->getName() . '</a></li>'; 
} 
?> 
</ol> 
</dd> 
</dl> 
<?php

} 
?>