Don't do a full rewrite ; it won't work, it has to be gradual. We were asked to do this (also PHP, no framework and around 1m LoC) a 2 years ago and we just qui

Don't do a full rewrite ; it won't work, it has to be gradual. We were asked to do this (also PHP, no framework and around 1m LoC) a 2 years ago and we just quietly refactored and containerised parts; the client is super happy but we actually didn't change that much. The major thing was that we didn't change/fix all the fragile stuff that was in there, we just added added microservices and packaged it up in docker. Now they can write new things with Laravel and react (their choice, not mine) and not worry about the old 'core' that runs a lot of stuff and gets called via API's.