We'd recommend installing composer in your own account. Installing composer is quite simple, and the instructions are provided by composer itself at https://getcomposer.org/
Because we provide several different php versions, you can choose which version to use.
PHP 5.6: /hsphere/shared/php56/bin/php-cli
PHP 7.0: /hsphere/shared/php70/bin/php-cli
PHP 7.1: /hsphere/shared/php71/bin/php-cli
And so on. Simply replace the "phpxx" bit with the version you require, for example, if you want to use PHP 7.2, simply use "php72", equally for PHP 5.3, use "php53".
You can create a symlink for this in your bin directory:
ln -s /hsphere/shared/php71/bin/php-cli ~/bin/php
After this, when you typed "php" it will refer to php 7.1.