Add the following line into your composer.json require block
"require": {
...
"oneflow/php-sdk": "dev-master"
}
Or run this command in your terminal
php composer.phar require oneflow/php-sdk:dev-master
git clone https://github.com/HPInc/oneflow-sdk-php <your-target-directory>
Download the .zip file of this project and unzip it in the desire location. Download the last zip here
You can find a lot of samples here.