You will need a working Symfony environment behind a web server (Apache, Nginx, and so on) and a relational database server such as MySQL or PostgreSQL. Some examples are based on using MongoDB but can be applied to other databases as well.
The book makes use of features available in Symfony 2.3 and higher. The examples might have to be adapted a bit if you are using an older version.
Some code also makes use of features available only in PHP 5.4 or higher, so they will need to be adapted to work with older versions of PHP.