Install Composer into Project on Centos [Quick Reference]

Navigate to project directory

curl -sS https://getcomposer.org/installer | php

Create a file in same directory named composer.json

Then add the required packages to the json file: (example)

{
"require": {
"psr/log": "1.0.0",
"phpunit/php-timer": "1.0.7",
"symfony/event-dispatcher": "3.0.0"
}
}

Once the json file has been edited and saved, execute the following:

php composer.phar install

This will download the appropriate packages.

Some packages include an autoloader and this can be included using a variation of the following:

require __DIR__ . '/vendor/autoload.php';

If you ever need to add packages or update packages you can run the following after editing the json file:

php composer.phar update

Source: https://www.vultr.com/docs/setup-composer-for-php-dependencies-on-centos-6