How can i update my products? - magento

Question

I want to update from my script the meta title, the meta description and the meta keywords for all of my products.
The meta title = the name of the product
The meta description = the short description of the product
The meta keywords is the meta keywords i've put from the category of the product.
I can loop and get the informations i want to make the update (except the meta keywords of the description) and after how i can make the update inside the loop ?
Thanks
<?php require_once 'app/Mage.php';
umask(0);
set_time_limit(0); // ignore php timeout
ignore_user_abort(true); // keep on going even if user pulls the plug*
while(ob_get_level())ob_end_clean(); // remove output buffers
ob_implicit_flush(true); // output stuff directly
//error_reporting(E_ALL);
/* not Mage::run(); */
Mage::app('default');
// get product collection (All product)
$storeId = Mage::app()->getStore()->getId();
$visibility = array(
Mage_Catalog_Model_Product_Visibility::VISIBILITY_BOTH,
Mage_Catalog_Model_Product_Visibility::VISIBILITY_IN_CATALOG);
$_productCollection = Mage::getResourceModel('catalog/product_collection')
->addAttributeToSelect('*')
->addAttributeToFilter('visibility', $visibility)
->setStoreId($storeId)
->addStoreFilter($storeId);
foreach ($_productCollection as $pro) { // loop each product
$meta_title = $pro['meta_title'];
$meta_description = $pro['meta_description'];
$name = $pro['name'];
$short_description = $pro['short_description'];
// I want to update the meta_title, meta_description, meta_keywords
// meta_description = short_description
// meta_title = name
// meta_keywords = meta keywords from the category of the product
}
?>

Answer 1

You can easy set keyword and description by using standard setters.
Inside foreach loop just use :
foreach ($_productCollection as $pro):
$product = Mage::getModel('catalog/product')->load($pro->getId());
$product->setMetaTitle('Product Title')
->setMetaKeyword('Product keywords')
->setMetaDescription('Product Description')
->save();
endforeach;

Answer 2

Try this,
foreach ($_productCollection as $pro):
$product = Mage::getModel('catalog/product')->load($pro->getId());
$cats = $product->getCategoryIds();
$meta_keys = '';
foreach ($cats as $category_id) {
$_cat = Mage::getModel('catalog/category')->load($category_id) ;
if($_cat->getMetaKeywords())
$meta_keys .= $_cat->getMetaKeywords().', ';
}
$product->setMetaTitle($pro->getName())
->setMetaKeyword($meta_keys)
->setMetaDescription($pro->getShortDescription())
->save();
endforeach;