website/includes/translation.php

<?php
// Translation system - Based on feedback system approach
require_once 'config.php';

class Translation {
    private static $translations = [];
    private static $current_lang = DEFAULT_LANGUAGE;
    
    public static function init($lang = 'en') {
        self::$current_lang = $lang;
        $lang_file = __DIR__ . "/../languages/{$lang}.php";
        
        if (file_exists($lang_file)) {
            self::$translations = require $lang_file;
        } else {
            // Fallback to English
            self::$current_lang = 'en';
            self::$translations = require __DIR__ . '/../languages/en.php';
        }
    }
    
    public static function get($key, $params = []) {
        if (!isset(self::$translations[$key])) {
            return $key; // Return key if translation not found
        }
        
        $translation = self::$translations[$key];
        
        if (!empty($params)) {
            foreach ($params as $placeholder => $value) {
                $translation = str_replace('{' . $placeholder . '}', $value, $translation);
            }
        }
        
        return $translation;
    }
    
    public static function getCurrentLang() {
        return self::$current_lang;
    }
    
    public static function getAvailableLanguages() {
        return [
            'en' => 'English',
            'fi' => 'Suomi'
        ];
    }
    
    public static function setLanguage($lang) {
        if (in_array($lang, array_keys(self::getAvailableLanguages()))) {
            self::init($lang);
            return true;
        }
        return false;
    }
    
    public static function getLanguageSwitcher($currentPath = '') {
        $current_lang = self::getCurrentLang();
        $languages = self::getAvailableLanguages();
        
        $switcher = '<div class="language-switcher">';
        $switcher .= '<span class="language-label">' . self::get('language') . ':</span>';
        
        foreach ($languages as $code => $name) {
            $separator = strpos($currentPath, '?') !== false ? '&' : '?';
            $switcherUrl = $currentPath . $separator . 'lang=' . $code;
            
            $class = $code === $current_lang ? 'active' : '';
            $switcher .= '<a href="' . htmlspecialchars($switcherUrl) . '" class="language-link ' . $class . '">' . $name . '</a>';
        }
        
        $switcher .= '</div>';
        return $switcher;
    }
}

// Helper function for easier translation access
function t($key, $params = []) {
    return Translation::get($key, $params);
}

// Auto-initialize with session language or default from config
if (session_status() === PHP_SESSION_NONE) {
    session_start();
}

// Handle language switching
if (isset($_GET['lang']) && in_array($_GET['lang'], array_keys(Translation::getAvailableLanguages()))) {
    $_SESSION['language'] = $_GET['lang'];
    Translation::setLanguage($_GET['lang']);
    
    // Redirect back to referring page or remove lang parameter
    $currentUrl = $_SERVER['REQUEST_URI'];
    $parsedUrl = parse_url($currentUrl);
    
    // Build URL without lang parameter
    $redirectUrl = $parsedUrl['path'];
    if (isset($parsedUrl['query'])) {
        parse_str($parsedUrl['query'], $queryParams);
        unset($queryParams['lang']); // Remove lang parameter
        
        if (!empty($queryParams)) {
            $redirectUrl .= '?' . http_build_query($queryParams);
        }
    }
    
    // Only redirect if not in CLI mode
    if (php_sapi_name() !== 'cli') {
        header('Location: ' . $redirectUrl);
        exit;
    }
}

// Initialize translation
$language = $_SESSION['language'] ?? DEFAULT_LANGUAGE;
Translation::init($language);
?>