Update to CMSB v. 8 from 3.56

I am going to have to update an old, complex application for a medical institution from v. 3.56 to the most current 3.8 version. Part of the change needed on the server is to move from PHP 7.4 to 8.1.

Also, the site depends upon a number of plugins to include createPDF, csvImport, formGenerator, newsletterBuilder, QRCode Generator, reportBuilder, showHideDependedentFieldsPlus, showHideFieldsForUsers, and websiteMembership. Can anyone share any problems they may have encountered with similar upgrades?

The hospital using this application depends upon it daily, and I will need to accomplish the change over a weekend and have a working version on the following Monday. I confess to being a bit nervous.