I need to change all my sites to php8.4 (or almost all). Is there a way to batch perform this change? Thanks!
You could try to change it in the database (web_domain table), change it manually for one site, compare the change, then apply it to the other sites, and finally use Tools > Resync in ISPConfig to apply the change. But I have not tested this, and it might not work or break things, so better to test it on a spare dev system first and not your live server.
