Install multiple versions off PHP on a Mac

php_on_mac.txt

# you can repeat this for any version of PHP available in brew

# adding needed taps
brew tap homebrew/php
brew tap homebrew/homebrew-php

# install php56 + mongodb and unlinking it
brew install php56
brew install homebrew/php/php56-mongodb  
brew unlink php56

# install php70 + mongodb and unlinking it
brew install php70
brew install homebrew/php/php70-mongodb  
brew unlink php70

# install php71 + mongodb and unlinking it
brew install php71
brew install homebrew/php/php71-mongodb  
brew unlink php71

#install php-version, a tool to fast switch versions
brew install php-version

#If you wish to swap the PHP you use on the command line, you should add the following to ~/.bashrc,
#~/.zshrc, ~/.profile or your shell's equivalent configuration file:
#This will enable php-version tool and set the default verion to 7.0.x (you can change the version of course)
source $(brew --prefix php-version)/php-version.sh && php-version 7.0

looks like this is deprecated now