Note: This is an already own answered question. It was made in order to help users facing the same problem in the future.
After I updated my Mac OS to Yosemite, my Phalcon Dev Tools stopped working and is giving this error:
Library not loaded: /usr/local/opt/icu4c/lib/libicui18n...How can I solve this?
Actually when updating to Yosemite it affects the PHP environment itself, so even running only the simple command $ php -v on the terminal will lead the same error message.
To solve this, if you have Homebrew installed you can follow these steps* on terminal:
brew reinstall pcre && brew unlink pcre && brew link pcre
brew reinstall php55
brew link php55
brew uninstall drush
brew install --HEAD drush* Solution from this SO answer.