Common Joomla errors caused after PHP update and how to fix them

OBS: we cannot edit the code of your website for you. If it is needed, you must either do this yourself or find a developer that can help you.

If after upgrading the PHP version, your website stopped working, you may find the following errors:

1. White page with the message "ERROR" - it is most likely to be caused by Joomla being out-of-date, or third-party extensions and/or templates also not compatible with newer PHP versions
2. You see error HTTP 500.

General troubleshooting the following step-by- step can help to solve the issue:

1. Revert the PHP version
2. Update your Joomla installation and extensions. A lot of extensions of Joomla 3 are not compatible with PHP 8.0 or above.
3. Try updating the PHP version again
4. If you still are experiencing any issues, you can enable errors_reporting, to see the exact error and try fixing it. 

The errors above are really generic. If the general troubleshooting doesn't work, you need to find more specific information enabling the error reporting.

Find the file configuration.php > change public $error_reporting = 'default';  to  public $error_reporting = 'maximum';

If you are not a web developer or has some knowledge regarding PHP you may need specialized help.