MAGENTO: COPY PRODUCTS FROM ONE CATEGORY TO ANOTHER CATEGORY

copy-products.php

<?php
require_once ( "app/Mage.php" );
umask(0);
 
// Initialize Magento
Mage::app();
 
$category = Mage::getModel('catalog/category');
$category->load('24'); // Category id you want to copy
$collection = $category->getProductCollection();
$collection->addAttributeToSelect('*');
foreach ($collection as $product) {
       $product->getId();// Now get category ids and add a specific category to them and save?
       $categories = $product->getCategoryIds();
       $categories[] = 29; // Category id you want to add
       $product->setCategoryIds($categories);
       $product->save();
}