Additional disable php functions list
I believe it would be a nice feature to add possibility in PHP Selector to add additional php function per user that you want to disable.
Right now you can add the "disable_functions" directive in /etc/cl.selector/php.conf file and it allows you to edit the function list which is disabled by default. Which is great, but it also may reduce security, since it allows to modify all the list.
What I would suggest is to create a new directive additionaldisablefunction_list.
What would it do? It would allow to manage additional disablefunction list. This could work like an extension to disablefunction, if you would add any additional functions, they would simply be added to the main disable_function list. You could add and remove them.
This could be a simple and safe way to add some restrictions per user when needed (for example disable mail function). And not so difficult to implement.