Roundcube detect old default system PHP version

Hi,
i have Ubuntu server 20.04. I want to change default php version from 7.4.33 to 8.3 and upgrade manually Roundcube 1.4.3(installed from ubuntu repo) to 1.6.9 (from source). I changed the default PHP version (update-alternatives...). Checking with php -v. Ok. It show PHP 8.3
But roudcube detect still old PHP 7.4.33 version. I removed,purged roundcube reinstall on the default PHP 8.3 but Roundcube (and the installer) detect still PHP 7.4.33. I create a phpfile (phpinfo()) in roundcube directory and show php 7.4.33
What is right way to correct this issue?
Thanks for your help.

 

Check its vhost or conf file as it could be fixed in there.

 

Thanks!
I enabled the new php conf in apache2. (a2enconf php8.3-fpm)
It works.