Oficial installation documentation.
sudo apt-get install fontconfig
cd /usr/local/share
wget https://bitbucket.org/ariya/phantomjs/downloads/phantomjs-2.1.1-linux-x86_64.tar.bz2
sudo tar xjf phantomjs-2.1.1-linux-x86_64.tar.bz2
sudo ln -s /usr/local/share/phantomjs-2.1.1-linux-x86_64/bin/phantomjs /usr/local/share/phantomjs; sudo ln -s /usr/local/share/phantomjs-2.1.1-linux-x86_64/bin/phantomjs /usr/local/bin/phantomjs; sudo ln -s /usr/local/share/phantomjs-2.1.1-linux-x86_64/bin/phantomjs /usr/bin/phantomjs
rm phantomjs-2.1.1-linux-x86_64.tar.bz2
mkdir ~/new-casperjs
cd ~/new-casperjs
npm install casperjs
node_modules/casperjs/bin/casperjs selftest