Add Related Product

 /**
     * 添加关联商品到指定商品
     */
    public function addRelatedProducts($product_id,$skus) {
    	$param = array();
    	
    	foreach ($skus as $key=>$sku) {
    		$related_product = Mage::getModel('catalog/product')->loadByAttribute('sku',$sku);
    		if ($related_product) {
    			$param[$related_product->getId()] = array('position'=>$key);
    		}
    	}
    	
    	$product = Mage::getModel('catalog/product')->load($product_id);
    	if ($product) {
    		$product->setRelatedLinkData($param)->save();
    		return true;
    	}
    	return false;
    }