Now that we have installed all the required software, we will proceed with the installation of Phalcon. Before we continue, we must install some dependencies:

$ sudo apt-get install php5-dev libpcre3-dev gcc make php5-mysql

For Windows systems and more details about how to compile the extension on different systems, please check the latest documentation at http://phalconphp.com/en/download.

Now, we can clone the repository and compile our extension:

$ git clone --depth=1 git://github.com/phalcon/cphalcon.git
$ cd cphalcon/build
$ sudo ./install
$ echo 'extension=phalcon.so' | sudo tee /etc/php5/mods-available/phalcon.ini

$ sudo php5enmod phalcon
$ sudo service php5-fpm restart

If everything goes well, you should be able to see Phalcon in the list of PHP installed modules:

$ php -m | grep phalcon