joomla plugin works correctly without caching and does not work with caching

Question

if caching is turned off then everything works correctly. if you enable caching, the plugin at the beginning works correctly, but after 5 minutes it stops processing the line. normal or progressive caching — it doesn’t matter. when you delete the cache — processing is turned on again, and again after 5 minutes it disappears. here is the complete plugin code. what could be the reason? code inserted into the material for example such {robokassa 5}

 class plgContentRobokassa extends JPlugin
{
    public $cont='';
    public function onContentPrepare($context, &$row, &$params, $page = 0)
    {
     $doc  = JFactory::getDocument();
     $doc->addStyleSheet(JURI::root(true).'/plugins/content/robokassa/css/robokassa.css');
     $this->cont=$context;
    }


    public function onAfterRender()
    {
 $is_test='0';
 $mrh_pass1='*****';
 $mrh_login='******';
        $app = JFactory::getApplication();
        if ($app->getName() != 'site') {
            return true;
        }

        // Получаем кодовое слово из параметров
        $varname = 'robokassa';

        //Получаем тело сайта
        $html = $app->getBody();

        // Если тегов нет
        if (strpos($html, $varname) === false)
        {
            return true;
        }
        $bodyPos = stripos($html, '<body');
        $preContent = '';
        if ($bodyPos > -1)
        {
            $preContent = substr($html, 0, $bodyPos);
            $html = substr($html, $bodyPos);
        }

        //Задаем шаблон поиска
        $pattern = '#\{' . $varname . ' ([0-9]+)\}#i';

        //Закидываем все найденные шаблоны в массив
        if (preg_match_all($pattern, $html, $matches))
        {
         $db = JFactory::getDbo();
         $query = $db->getQuery(true);
            foreach ($matches[0] as $i => $match)
            {
                *replace code here*
            }
             $html=$preContent.$html.$script_alert;
            //Запихиваем всё обратно в тело
            $app->setBody($html);
        }
    }
}

Answer 1

The plugin events are invoked in the order they have in the Plugin administration. Cache is part of the System plugins so when their cache is valid the response is retrieved from Cache, and the plugins which come before it are not executed.

You could be able to solve this by moving your plugin after Cache (or last)

If the plugin is of a different kind, i.e. Content, there is no way to achieve this.

You can change it into a System plugin (all events from any plugin category is available also in the System plugins).

Another alternative, you could put your code in a module, prevent caching in the module; but this will not work with page cache.

Finally, and I don't know why I didn't write it first, make an Ajax call to a page which you will NOT cache (by excluding it in the page cache plugin configuration: that way the page will be cached and each time it will retrieve the current data.