Update PhP version in Homestead?

Question

virtual box

vagrant box update
vagrant ssh
sudo apt-get update
sudo apt-get upgrade

then I go to composer and change the version from 7.1.9 to 7.2.0, I do composer update, it gives an error:

$ composer update
Loading composer repositories with package information
Updating dependencies (including require-dev)
Your requirements could not be resolved to an installable set of packages.

  Problem 1
    - This package requires php ^7.2.0 but your PHP version (7.1.9) does not satisfy that requirement.

Yes, I know what he writes, I don’t understand why the version upgrade didn’t pass. Of course, you can manually get into the homestead image, but is it necessary, because this is a vendor, it will fly off with an update, and why do I need a homestead then.