Using Joomla can be a smooth experience. However, there can be times when components or modules exhibit PHP errors. There are many reasons why such problems can occur. In order to find the source of such a problem, you may want to track recent file or server changes.
One problem which could pose problems is upgrading the Apache server. For example, you may want to add a php module like xmlrpc. However, the default upgrade settings in web host manager or Linux CentOS could upgrade the PHP from the current version to a much more recent version. After the upgrade is completed, some extensions and modules which were created in an older PHP version may not work properly with the new version since some functions and features could be deprecated. To solve the issue, you may want to create a new Apache upgrade with the previous version of PHP for which everything worked properly, or upgrade Joomla core, components and modules, if necessary. Unfortunately, some older plugins, modules and components will be more difficult to upgrade than others.