How To install Phalcon on Ubuntu 14.04 LTS (by @jaromirfojtu)

Install the requirements for Phalcon.

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

Clone the framework repo onto your system.

$ git clone git://github.com/phalcon/cphalcon.git

Compile extension.

$ cd cphalcon/build
$ sudo ./install

Add extension to PHP and enable phalcon

$ sudo echo "extension=phalcon.so" >> /etc/php5/mods-available/phalcon.ini
$ sudo php5enmod phalcon

Restart Apache2

$ sudo service apache2 restart

Install specific version.

$ git tag

phalcon-v1.3.3
phalcon-v1.3.4
phalcon-v2.0.0
phalcon-v2.0.7
phalcon-v2.0.8

$ git checkout tag/phalcon-v2.0.0

Install 2.0.2 version

$ wget https://github.com/phalcon/cphalcon/archive/phalcon-v2.0.2.tar.gz
$ tar xvzf phalcon-v2.0.2/
$ cd build/
$ sudo ./install