Hi, I have personally only fully tested CodeIgniter 3 with PHP 7.3.x, but there are members runnit it with PHP 7.4. There are one bug that triggers E_DEPRECATED, that's fixed in 3.1.12 (not yet released). But no known issues that are breaking the system.
You should check out CodeIgniter 4, it's made for PHP 7.2 and up.
