Install Composer on Debian

sudo apt-get install curl php5-cli
 curl -sS https://getcomposer.org/installer | sudo php -- --install-dir=/usr/local/bin --filename=composer

Verify installation:

composer --version
Composer version 4ecdbf89c4a3d1e5dfe73c57e3202a5e2a18c87e 2014-07-28 20:12:27