How to set and use a global variable within a content plugin?

Question

It's probably a duplicate. Anyhow, I am writing a J5 content plugin using onContentPrepare event. It turns out, that this plugin is called several times before the page is sent to the browser. I want to execute a short code only during the first call and any subsequent plugin calls to check that flag. For that reason, I need a flag to be reset before the first call and set on the first code execution. What is the best way to achieve this? Some kind of global variable?

Answer 1

Normally plugins in Joomla are instantiated only once per request. So using a class member variable is the cleanest solution:

use Joomla\CMS\Event\Content\ContentPrepareEvent;
use Joomla\CMS\Plugin\CMSPlugin;

final class MyPlugin extends CMSPlugin
{
    private bool $flag = false;

    public function onContentPrepare(ContentPrepareEvent $event)
    {
        // Check if flag has been set.
        if (!$this->flag)
        {
            // Set the flag on first run.
            $this->flag = true;

            // Code that will be executed once.
        }

        // Code that will be executed every time.
    }
}