Store View – Language Switch on Product Page Returns 404

The following approach might be not very SEO friendly but with different URL keys I don't see any SEO friendly one.

You can setup a proxy page like this:

<?php

require_once 'app/Mage.php';
umask(0);

Mage::run();

$_product = Mage::getModel('catalog/product')->load((int)$_REQUEST['id']);
if ($_product->getId()) {
    header('Location: ' . $_product->getProductUrl());
}

Then in your WP you can just link to this file specifying product ID as _GET parameter.

Unfortunately, none of the efficient ways to update a product attribute work in this case. $product->getResource()->saveAttribute() updates the attribute for all store views even if you set the store ID on the $product object. Mage::getSingleton('catalog/product_action')->updateAttributes() only updates the value in a specific store, but it cannot set the attribute to use the default value (see also this Stack Overflow question for a reference). Hence, we have to use the slow, memory intensive way via $product->save().

I assume that you know which attributes you would like to update. For the following example, I set the visibility attribute to use the default value. The following script should then do the trick (make sure you change it according to your needs):

<?php

error_reporting(E_ALL);
ini_set('display_errors', '1');

require_once 'app/Mage.php';
Mage::app()->setCurrentStore(Mage_Core_Model_App::ADMIN_STORE_ID);
set_time_limit(0);

function useDefaultValueCallback($args)
{
    // change to the ID of your french store view
    $specificStoreViewId = 7;
    $product = Mage::getModel('catalog/product');
    $product->setData($args['row']);
    $product->setStoreId($specificStoreViewId);
    // change according to your needs
    $product->setData('visibility', false);
    $product->save();
}

$products = Mage::getModel('catalog/product')->getCollection();
Mage::getSingleton('core/resource_iterator')->walk($products->getSelect(), array('useDefaultValueCallback'));