src/I18n/I18N.php
public function init()
    {
        parent::init();
        if (empty($this->languages)) {
            $this->languages = [Reaction::$app->language];
        }
        $this->initUrlLanguagePrefixes();
        if (!isset($this->translations['rct']) && !isset($this->translations['rct*'])) {
            $this->translations['rct'] = [
                'class' => 'Reaction\I18n\PhpMessageSource',
                'sourceLanguage' => 'en-US',
                'basePath' => '@reaction/Messages',
            ];
        }

        if (!isset($this->translations['app']) && !isset($this->translations['app*']) && !isset($this->translations['*'])) {
            $this->translations['app'] = [
                'class' => 'Reaction\I18n\PhpMessageSource',
                'sourceLanguage' => Reaction::$app->sourceLanguage,
                'basePath' => '@app/Messages',
            ];
        }
    }
public function init()
    {
        parent::init();
        if (empty($this->languages)) {
            $this->languages = [Reaction::$app->language];
        }
        $this->initUrlLanguagePrefixes();
        if (!isset($this->translations['rct']) && !isset($this->translations['rct*'])) {
            $this->translations['rct'] = [
                'class' => 'Reaction\I18n\PhpMessageSource',
                'sourceLanguage' => 'en-US',
                'basePath' => '@reaction/Messages',
            ];
        }

        if (!isset($this->translations['app']) && !isset($this->translations['app*']) && !isset($this->translations['*'])) {
            $this->translations['app'] = [
                'class' => 'Reaction\I18n\PhpMessageSource',
                'sourceLanguage' => Reaction::$app->sourceLanguage,
                'basePath' => '@app/Messages',
            ];
        }
    }
Initializes the component by configuring the default message categories.