"Deprecated: Joomla\Input\Input ..." after upgrading PHP8.0 to PHP8.1 in Joomla 3.10.11

Question

I have updated the PHP version from 8.0 to 8.1.0 and my Joomla version is 3.10.11. Now I am getting deprecated warning such as:

Deprecated: Joomla\Input\Input implements the Serializable interface, which is deprecated. Implement __serialize() and __unserialize() instead (or in addition, if support for old PHP versions is necessary)

and

Deprecated: Return type of Joomla\Input\Input::count() should either be compatible with Countable::count(): int, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice...

I have updated the modules and plugins, but am still getting those warnings. Have you faced such issues? Is there a fixed version available? (I want to use the Joomla version 3.10.11 with PHP 8.1)

Answer 1

Edit the file configuration.php and set Error Reporting to filter Deprecated messages:

public $error_reporting = 'simple';

Check the behaviour of third party extensions in a test environment because they may have issues with PHP 8.1.

The recommended version of PHP for Joomla 3.x is 8.0 - ref. Joomla Technical Requirements