code: public function addTextContainer($name, $content, $language)
      {
          $allTexts = $this->getPageTexts($language);
          if (isset($allTexts[$name])) {
              throw new \Exception("Text container name already used.");
          }
          $this->contents[$language][$name] = array(
              'id'       => $name,
              'name'     => $name,
              'content'  => $content,
              'outdated' => false
          );
          $this->writeTextsToFile($language);
          if ($language === $this->baseLang) {
              $this->setExtraLanguagesOutdated($name, $content);
          }
  
          return $this->contents[$language][$name];
      }
docs: Adds a new text container.
  
  @param string $name
  @param string $content
  @param string $language
  @return array
  @throws \Exception