Thanks for the request. It should be easy to add the XOAUTH2 mechanism to the AUTHENTICATE step of imap_open, but consumers will need to add OAuth flows to their application; that's the hard part.

Because Google and Microsoft are switching to OAuth soon, and since there may be some developers who have questions on how to put it all together, we've assembled a single resource (info, plan, status, etc) for consumers: https://wiki.php.net/todo/ext/imap/xoauth2

It's a work in progress.

Hello, is there any news on this feature? On May 30th 2022, Google will shut down the possibility to use password authentication, with only a few exceptions, which may cover some use cases, but not all. Having imap_open support XOAUTH2 would be a big help for existing applications using imap_* functions.

Hello, is there any news about this feature? 
In the meantime, Microsoft has also completely discontinued the operation for standard IMAP for their entire Exchange-Online and Office365 structure.
This means that the PHP-IMAP implementation can unfortunately no longer be used for the major providers :(

As far as I understand it correctly, only a different base64 / AUTH mechanism would have to be implemented. So that you provide a token instead the user password.

See Microsoft documentation:
learn.microsoft.com/de-de/exchange/client-developer/legacy-protocols/how-to-authenticate-an-imap-pop-smtp-application-by-using-oauth#sasl-xoauth2
 
For me, it would also be a great help for existing applications to be able to use the native imap_* functions.