Firstly install Brew on your MAC

* ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"

Then install PHP

* brew update
* brew tap homebrew/dupes
* brew tap homebrew/php
* brew install php56
* brew install composer

to test installation, runs:

```
$ composer -V

Composer version 1.1.2 2016-05-31 19:48:11
```