src/Reaction.php
public static function tp($category, $message, $params = [], $language = null)
    {
        $translationPromise = new \Reaction\I18n\TranslationPromise($category, $message, $params, $language);
        return $translationPromise;
    }
public static function tp($category, $message, $params = [], $language = null)
    {
        $translationPromise = new \Reaction\I18n\TranslationPromise($category, $message, $params, $language);
        return $translationPromise;
    }
Translates a message to the specified language.
Looks like a ::t() method but returns a TranslationPromise for further translation when request language will known

@param string $category Message category
@param string $message  Message for translation
@param array  $params   Parameters array
@param string $language Language translate to
@return \Reaction\I18n\TranslationPromise