Macにcomposerをbrewでインストール

What?

• これじゃインストールできない

$ brew install composer
...
Error: No similarly named formulae found.
==> Searching taps...
These formulae were found in taps:
homebrew/php/composer                                             Caskroom/cask/multimarkdown-composer
homebrew/php/composer@1.2                                         Caskroom/versions/multimarkdown-composer-beta
Caskroom/cask/multimarkdown-composer-pro
To install one of them, run (for example):
  brew install homebrew/php/composer

How to?

$ brew install homebrew/php/composer