/*
Plugin Name: Query the categories in all langages with Polylang
*/

add_filter('request', 'pll_cat_request');
function pll_cat_request($request) {
	// default permalinks
	if (isset($request['cat']))
		$cat = $request['cat']; 

	// pretty permalinks
	if (isset($request['category_name'])) {
		$cat = get_category_by_slug($request['category_name']);
		$cat = $cat->term_id;
		unset($request['category_name']);
	}

	if (!isset($cat))
		return $request; // end here if the request is not a category

	// get the category in all languages
	global $polylang;
	foreach ($polylang->get_languages_list() as $lang)
		$cats[] = pll_get_term($cat, $lang);

	$request['cat'] = implode(',', $cats);
	return $request;
}