wget https://bitbucket.org/ariya/phantomjs/downloads/phantomjs-2.1.1-linux-x86_64.tar.bz2
tar xvf phantomjs-2.1.1-linux-x86_64.tar.bz2
sudo cp phantomjs-2.1.1-linux-x86_64/bin/phantomjs /usr/local/bin
Reference:
http://sameerhalai.com/blog/how-to-install-phantomjs-on-a-centos-server/