index-shop/site/snippets/sitemap.php

<?= '<?xml version="1.0" encoding="UTF-8"?>' ?>
<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9"
        xmlns:xhtml="http://www.w3.org/1999/xhtml">
<?php
$site = site();
$kirby = kirby();

// Static pages
$pages = $site->index()->filterBy('template', 'in', ['home', 'error', 'thanks']);

foreach ($pages as $p) {
  foreach ($kirby->languages() as $lang) {
    $url = $p->url($lang->code());
?>
  <url>
    <loc><?= $url ?></loc>
    <lastmod><?= $p->modified('c', 'date') ?></lastmod>
    <changefreq>monthly</changefreq>
    <priority><?= $p->isHomePage() ? '1.0' : '0.8' ?></priority>
    <?php foreach ($kirby->languages() as $altLang): ?>
    <xhtml:link rel="alternate" hreflang="<?= $altLang->code() ?>" href="<?= $p->url($altLang->code()) ?>" />
    <?php endforeach ?>
  </url>
<?php
  }
}

// Virtual product pages from Shopify
$products = getShopifyProducts();
foreach ($products as $product) {
  foreach ($kirby->languages() as $lang) {
    $url = $lang->code() == 'fr'
      ? $site->url() . '/' . $product['handle']
      : $site->url() . '/en/' . $product['handle'];
?>
  <url>
    <loc><?= $url ?></loc>
    <lastmod><?= date('c') ?></lastmod>
    <changefreq>weekly</changefreq>
    <priority>0.9</priority>
    <?php foreach ($kirby->languages() as $altLang): ?>
    <?php
      $altUrl = $altLang->code() == 'fr'
        ? $site->url() . '/' . $product['handle']
        : $site->url() . '/en/' . $product['handle'];
    ?>
    <xhtml:link rel="alternate" hreflang="<?= $altLang->code() ?>" href="<?= $altUrl ?>" />
    <?php endforeach ?>
  </url>
<?php
  }
}
?>
</urlset>