Component.php

<?php

namespace nhockizi\languagepicker;

use Yii;

class Component extends \yii\base\Component
{
    
    /**
     * @var function - function to execute after changing the language of the site.
     */
    public $callback;

    /**
     * @var integer expiration date of the cookie storing the language of the site.
     */
    public $expireDays = 30;

    /**
     * @var string Name of the cookie.
     */
    public $cookieName = 'language';

    /**
     * @var string The domain that the language cookie is available to.
     * For details see the $domain parameter description of PHP setcookie() function.
     */
    public $cookieDomain = '';

    /**
     * @var array List of available languages
     *  Formats supported in the pre-defined skins:
     * 
     * ~~~
     *  ['en', 'de', 'es']
     *  ['en' => 'English', 'de' => 'Deutsch', 'fr' => 'Français']
     *  ['en-US', 'de-DE', 'fr-FR']
     *  ['en-US' => 'English', 'de-DE' => 'Deutsch', 'fr-FR' => 'Français']
     * ~~~
     * 
     */
    public $languages;

    /**
     * @inheritdoc
     * @param array $config
     * @throws \yii\base\InvalidConfigException
     */
    public function __construct($config = array())
    {

        if (empty($config['languages'])) {
            throw new \yii\base\InvalidConfigException('Missing languages');
        } else if (is_callable($config['languages'])) {
            $config['languages'] = call_user_func($config['languages']);
        }

        parent::__construct($config);
    }

    /**
     * @inheritdoc
     */
    public function init()
    {

        $this->initLanguage();

        parent::init();
    }

    /**
     * Setting the language of the site.
     */
    public function initLanguage()
    {
        if (isset($_GET['language-picker-language'])) {
            if ($this->_isValidLanguage($_GET['language-picker-language'])) {
                return $this->saveLanguage($_GET['language-picker-language']);
            } else if (!Yii::$app->request->isAjax) {
                return $this->_redirect();
            }
        } else if (Yii::$app->request->cookies->has($this->cookieName)) {
            if ($this->_isValidLanguage(Yii::$app->request->cookies->getValue($this->cookieName))) {
                Yii::$app->language = Yii::$app->request->cookies->getValue($this->cookieName);
                return;
            } else {
                Yii::$app->response->cookies->remove($this->cookieName);
            }
        }

        $this->detectLanguage();
    }

    /**
     * Saving language into cookie and database.
     * @param string $language - The language to save.
     * @return static
     */
    public function saveLanguage($language)
    {

        Yii::$app->language = $language;
        $this->saveLanguageIntoCookie($language);

        if (is_callable($this->callback)) {
            call_user_func($this->callback);
        }

        if (Yii::$app->request->isAjax) {
            Yii::$app->end();
        }

        return $this->_redirect();
    }

    /**
     * Determine language based on UserAgent.
     */
    public function detectLanguage()
    {
        $acceptableLanguages = Yii::$app->getRequest()->getAcceptableLanguages();
        foreach ($acceptableLanguages as $language) {
            if ($this->_isValidLanguage($language)) {
                Yii::$app->language = $language;
                $this->saveLanguageIntoCookie($language);
                return;
            }
        }

        foreach ($acceptableLanguages as $language) {
            $pattern = preg_quote(substr($language, 0, 2), '/');
            foreach ($this->languages as $key => $value) {
                if (preg_match('/^' . $pattern . '/', $value) || preg_match('/^' . $pattern . '/', $key)) {
                    Yii::$app->language = $this->_isValidLanguage($key) ? $key : $value;
                    $this->saveLanguageIntoCookie(Yii::$app->language);
                    return;
                }
            }
        }
    }

    /**
     * Save language into cookie.
     * @param string $language
     */
    public function saveLanguageIntoCookie($language)
    {
        $cookie = new \yii\web\Cookie([
            'name' => $this->cookieName,
            'domain' => $this->cookieDomain,
            'value' => $language,
            'expire' => time() + 86400 * $this->expireDays
        ]);

        Yii::$app->response->cookies->add($cookie);
    }

    /**
     * Redirects the browser to the referer URL.
     * @return static
     */
    private function _redirect()
    {
        $redirect = Yii::$app->request->absoluteUrl == Yii::$app->request->referrer ? '/' : Yii::$app->request->referrer;
        return Yii::$app->response->redirect($redirect);
    }

    /**
     * Determines whether the language received as a parameter can be processed.
     * @param string $language
     * @return boolean
     */
    private function _isValidLanguage($language)
    {
        return is_string($language) && (isset($this->languages[$language]) || in_array($language, $this->languages));
    }

}