Magento get related products by product id

Magento displays related products block in product page default. If u would like to display this block in other page, u need to customize this block.

<?php

  

//load a product resources

$_product = Mage::getModel('catalog/product')->load($productId);

  

//save the product into the registry

Mage::register('product', $_product);

  

//call $_product's related products

echo $this->getLayout()->createBlock('catalog/product_list_related')->setTemplate('catalog/product/list/related.phtml')->toHtml();

  

?>