Run the following Homebrew commands to install PHP and MySQL

# brew update
# brew install php56
# brew install mysql
# mysql.server start

test with `/usr/local/Cellar/php56/5.6.0/bin/php --version` (test)
edit `~/.config/fish/fish.config` or `~/.bash_profile`
add the line `alias php='/usr/local/Cellar/php56/5.6.0/bin/php'`
test with `php --version` (should yield `PHP 5.6.0 (cli)`)