Here's another option, from the guys from liip, here. This is a PHP package that comes pre-built for Yosemite (older versions works too) but it is just one line of code:
curl -s http://php-osx.liip.ch/install.sh | bash -s 5.6
After that, everything is ready to work as expected. The configuration that cames with that installation is well suited for Symfony 2 development, but it should work just fine with other use cases.
Finally, if you need to use the updated PHP CLI, too, but you don't want to use the PHP version that comes with the OS, then you could also add to your .bash_profile or similar this line of code:
export PATH=/usr/local/php5/bin:$PATH