PHP extensions (from PECL) can be very handy when you need them. Unfortunately, not all distributions come with packages that will install them for you...this is where compiling comes in. On the SitePoint PHP blog Bruno Skvorc has posted a guide to compiling extensions from source to help you get started.
Sometimes it's hard to know which PHP extensions you'll need before you install PHP. In cases where you need to add extensions later on, you might get lucky and the extension could be in the repository of the OS you're using. [...] What if there's no such thing for other extensions, though? In this tutorial, we'll go through installing some custom extensions on Linux systems (and OS X - the process is nearly identical).
He uses a Laravel Homestead instance as a platform for his example and shows the compilation of the MongoDB for PHP driver. He walks you through the process of booting up the VM and getting the environment/required packages installed. He then shows the process for the installation of two different kinds of PHP extensions: internal and third-party. Finally he shows you how to update your configuration, load in the compiled extension and test it (in this case looking at the phpinfo() to ensure it's loaded).