Use Homebrew/core instead of Homebrew/php
brew install php@5.6 --with-pear
brew install php@7.0 --with-pear
brew install php@7.1 --with-pear
brew install php@7.2 --with-pear
Also, you may have the need to tweak configuration settings of PHP to your needs. A common thing to change is the memory setting, or the date.timezone configuration. The php.ini files for each version of PHP are located in the following directories: