Magento - Set all categories to be an anchor

Magento Category Anchors

IMPORTANT NOTE: To have this work you cannot have Flat Catalog enabled

// ORIGINAL -----------------------

<?php 
error_reporting(E_ALL);
ini_set('display_errors', '1');
 
// Load Up Magento Core
define('MAGENTO', realpath(''));

require_once(MAGENTO . '/app/Mage.php');
 
$app = Mage::app();
 
$categories = Mage::getModel('catalog/category')
 ->getCollection()
 ->addAttributeToSelect('*')
 ->addAttributeToFilter('is_anchor', 0)
 ->addAttributeToFilter('entity_id', array("gt" => 1))
 ->setOrder('entity_id')
 ;
 
foreach($categories as $category) {
 echo $category->getId() . "\t" . $category->getName() . "\n";
 $category->setIsAnchor(1);
 $category->save();
}
?>

// END ORIGINAL ------------------------------------

// MODIFIED -----------------------------------

<?php
error_reporting(E_ALL);
ini_set('display_errors', '1');
// Load Up Magento Core
define('MAGENTO', realpath(''));

require_once(MAGENTO . '/app/Mage.php');
$app = Mage::app();
$categories = Mage::getModel('catalog/category')
->getCollection()
->addAttributeToSelect('*')
// ->addAttributeToFilter('is_anchor', '0')
->addAttributeToFilter('entity_id', array("gt" => 1))
->setOrder('entity_id')
;

foreach($categories as $category) {
echo $category->getId() . "\t" . $category->getName() . "\t" . $category->getIsAnchor() . "\n";
$category->setIsAnchor(1);
echo $category->getId() . "\t" . $category->getName() . "\t" . $category->getIsAnchor() . "\n";
$category->save();
// echo $category->getId() . "\t" . $category->getName() . "\t" . $category->getIsAnchor() . "\n";
}
?>

THIS IS MAGENTO 1