Composer and Archlinux.

Here the recipe:

• install this packages:

pacman -S extra/php

pacman -S extra/php-composer 1.0.0.alpha11-1

pacman -S extra/php-imap

• edit the file: /etc/php/php.ini

uncomment two lines:

openssl.so and phar.so

• do a whereis composer:

j3nnn1@seventhtransept home$ whereis composer
composer: /usr/bin/composer

• and edit again the /etc/php/php.ini to add the new path directory in the variable  open_basedir
  

And that's all folks!