$ brew update
$ brew install homebrew/php/php71
~/.bashrc
に
export PATH="$(brew --prefix homebrew/php/php71)/bin:$PATH"
を追記
からの
$ source ~/.bashrc
$ php -v
すると
PHP 7.1.6 (cli) (built: Jun 23 2017 08:42:20) ( NTS ) Copyright (c) 1997-2017 The PHP Group Zend Engine v3.1.0, Copyright (c) 1998-2017 Zend Technologies
乙