On CBI, set variable in on_init and use it on on_before_commit

Hi everyone.

I'm working with CBI files and I'm currently trying to see, when my user clicks on Save and Apply, if a value has changed.

I'm reading the existing (or not) value from the file on on_init and store it on a gobal variable, but the variable is unset on on_before_commit.

Is there a way to persist a value in this case, without having to write any additional option on the config file? Or is there a way to simply check if the value has changed when commiting?

I'm beginning with OpenWRT and Lua. Thanks in advance!