The sabre/xml library is a specialized XML reader and writer.
Major version 3 implements type declarations for input parameters, function returns, variables etc. It supports PHP 7.4 and PHP 8. When you upgrade to major version 3, if you extend classes etc., then you will need to make similar type declarations in your code.
Head over to the SabreDAV mailing list for any questions.
This library is being developed by fruux. Drop us a line for commercial services or enterprise support.