http://getcomposer.org/doc/00-intro.md#using-composer

$ brew install josegonzalez/php/composer

出现错误：

composer: Missing PHP53, PHP54 or PHP55 from homebrew-php. Please install one of them before continuing

composer安装提示：

Note: If you receive an error saying PHP53 or higher is missing use this command to install php brew install php53-intl

执行$ brew install php54-intl 提示：

Error: No available formula for zlib
Please tap it and then try again: brew tap homebrew/dupes
Searching taps…

执行$ brew tap homebrew/dupes

再执行：$ brew install josegonzalez/php/composer

参考：http://www.torounit.com/blog/category/php/