1) Update & Upgrade brew

brew update && brew upgrade

2) To install, run this command.

brew install php@a.b
# E.g.
brew install php@8.3

3) To upgrade, run this command.

brew upgrade php@a.b
# E.g.
brew upgrade php@8.3

4) Check your upgrade

which php
php -v

5) Restart the service if needed

brew services restart php

If you are using the PHP in IDE such as PHPStorm, remember to update the Path.

(Before)

(After)