Wordpress Basic Translation Functions, URL, Session, Localization Domain Setup. Multilanguage

csdev-lang.php

<?php

/**
 * WP THEME MULTILINGUAL SUPPORT    
 * Used with Bootscore, WooCommerce
 * Based on https://gist.github.com/l2aelba/5244912
 * Version 1.0 - 5mar2022
 * Version 2.0 - 27apr2022
 * csdev
 * NOTE: require this file from functions.php or integrate
 **/

/**
 * Array of supported languages, first is default
 */
function csdev_langs()
{
    return array('en', 'es', 'it');
}

function csdev_default_lang()
{
    $langs = csdev_langs();
    return $langs[0];
}

/**
 * Translate page title blindly
 * Setup domain, here using Bootscore
 */
function csdev_page_title($page_title)
{
    return __($page_title, 'bootscore');
}
add_filter('woocommerce_page_title', 'csdev_page_title', 10, 1);

/**
 * No home canonical redirect
 * Also force WooCommerce Plugin Domain & Theme Domain reload
 */
add_action('template_redirect', function () {
    if (is_front_page()) {
        remove_action('template_redirect', 'redirect_canonical');
    }
    // reload woo domain with correct language
    wc()->load_plugin_textdomain();
    // reload theme domain
    load_theme_textdomain('bootscore', get_template_directory() . '/languages');
}, 0);

/**
 * Add rewrite rules for languages
 * Still in development
 */
function csdev_lang_rewrite_rule()
{

    $custom_types = ["product"];

    // categories AT TOP?
    foreach (csdev_langs() as $lang) {
        add_rewrite_rule(
            "^$lang/product-category/(.+?)/?$",
            'index.php?product_cat=$matches[1]&lang=' . $lang,
            'top'
        );
        
        // /product-category/CATEGORY/CATEGORY1
        add_rewrite_rule(
            "^$lang/product-category/(.+?)/page/?([0-9]{1,})/?$",
            'index.php?product_cat=$matches[1]&paged=$matches[2]&lang=' . $lang,
            'top'
        );

    }


    // Product post Individual
    foreach (csdev_langs() as $lang) {

        // home
        add_rewrite_rule(
            "^$lang" . '/?$',
            'index.php?pagename=home&lang=' . $lang,
            'top'
        );

        // home too
        add_rewrite_rule(
            "^$lang/home",
            'index.php?pagename=home&lang=' . $lang,
            'top'
        );

        // shop
        add_rewrite_rule(
            "^$lang" . '/shop',
            'index.php?post_type=product&lang=' . $lang,
            'top'
        );

        foreach ($custom_types as $type) {
            // Custom Post Individual
            add_rewrite_rule(
                "^$lang/" . $type . '/([^/]*)/?$',
                'index.php?lang=' . $lang . '&' . $type . '=$matches[1]',
                'top'
            );
        }
    }


    // pages AT THE END after custom post    
    foreach (csdev_langs() as $lang) {

        // example: for my-account/edit-address/facturacion
        // pagename=my-account&edit-address=facturacion
        add_rewrite_rule(
            "^$lang/([^/]*)/?/([^/]*)/?/([^/]*)/?",
            'index.php?pagename=$matches[1]&$matches[2]=$matches[3]&lang=' . $lang,
            'top'
        );
        // example: for my-account/edit-address
        add_rewrite_rule(
            "^$lang/([^/]*)/?/([^/]*)/?",
            'index.php?pagename=$matches[1]&$matches[2]&lang=' . $lang,
            'top'
        );
        // example: for /my-account
        add_rewrite_rule(
            "^$lang/([^/]*)/?",
            'index.php?pagename=$matches[1]&lang=' . $lang,
            'top'
        );        
    }

  
    // eliminate in production!    
    flush_rewrite_rules(true);
}
add_action('init', 'csdev_lang_rewrite_rule');

/**
 * Add current language to menu items
 * Translate title "blindly" (enter string in .POT)
 */
function csdev_change_menu($items)
{
    foreach ($items as $item) {
        $item->url   = csdev_get_lang_url($item->url);
        $item->title = __($item->title, "bootscore");
    }
    return $items;
}
add_filter('wp_nav_menu_objects', 'csdev_change_menu', 10, 2);

/**
 * Get any relative url for lang 
 * ie /en/product-category/wines/alfredo-roca
 * $url shouldn't contain a $lang segment!
 */
function csdev_get_lang_url($url, $lang = false)
{       
    $lang     = $lang ?: csdev_get_lang();
    $root     = get_bloginfo("url");
    
    // remove root from url    
    $thisurl  = str_replace($root, "", $url);
    
    // determine if language is in first segment, remove it
    $segments = explode('/', parse_url(ltrim($thisurl,"/"), PHP_URL_PATH));
    $segment  = $segments[0] ?? null;       
    if (in_array($segment,csdev_langs())) {
        // language found, remove
        $thisurl = substr($thisurl,3);        
    }              
    $url      = $root . "/" . $lang . $thisurl;
    return $url;
}

/**
 * Set text domain for plugins & theme
 * TODO: Implement more languages
 */
function csdev_set_locale($locale)
{
    global $locale;
    $lang  = csdev_get_lang();
    if ($lang == 'es')
        $locale =  'es_AR';
    elseif ($lang == 'en')
        $locale = 'en_US';
    elseif ($lang == 'it')
        $locale = 'it_IT';        

    return $locale;
}
add_filter('locale', 'csdev_set_locale', 10, 1);

/**
 * Session
 */
function csdev_init_session()
{
    if (!session_id()) {
        session_start();
    }
    // don't set default language or it will overwrite if it's already set
}
add_action('init', 'csdev_init_session', 1);

/**
 * Set lang in session (from url or forced)
 */
function csdev_set_lang($lang = false)
{

    // do not refresh page
    $_SESSION['refresh'] = false;

    // current session language
    $session_lang = $_SESSION['lang'] ?? false;

    // parameter or else url
    $lang  = $lang ?:  get_query_var('lang', '');
    $langs = csdev_langs();
    if (in_array($lang, $langs)) {
        // if valid language, save it to session only if different
        if ($session_lang !== $lang) {
            $_SESSION['lang']    = $lang;
            $_SESSION['refresh'] = true;
        }
    } else {
        // invalid parameter or url language, use current or default and rectify url
        if (!$session_lang) {
            $_SESSION['lang']    = csdev_default_lang();
        }

        // redirect to correct url        
        wp_redirect(csdev_get_current_lang_url(), 301);
    }


    // set domains  
    return $_SESSION['lang'];
}

/**
 * Current URL for a certain language (or current if false)
 */
function csdev_get_current_lang_url($lang =false) 
{
    global $wp;
    return csdev_get_lang_url(home_url($wp->request),$lang);
}

/**
 * Clean up buffer at init
 */
function output_buffer()
{
    ob_start();
}
add_action('init', 'output_buffer', 2);

/**
 * Header calls
 */
function csdev_lang_header()
{
    csdev_set_lang();
    /* Refresh if new language */
    if ($_SESSION['refresh']) {
        error_log("REFRESH " . $_SESSION['lang']);
        header("Refresh:0");
        $_SESSION['refresh'] = false;
    }
}
add_action('wp_head', 'csdev_lang_header', 0);

/**
 * Get current lang
 */
function csdev_get_lang()
{
    return $_SESSION['lang'] ?? csdev_default_lang();
}


/**
 * Whitelist "?lang"
 */
add_filter('query_vars', function ($query_vars) {
    $query_vars[] = 'lang';
    return $query_vars;
});