How to install PHP intl extension in Ubuntu 14.04

I have a hard time to find exact method to install PHP intl extension in **Ubuntu 14.04**. I tried with `sudo apt-get install php5-intl` but displays error `Unable to locate package`. I really need this extension for Zend Framework 2 , because of above missing extension I am getting error like this **ERROR:** `Zend\I18n\Validator component requires the intl PHP extension` I am using PHP 5.5.9. How can I install `PHP-intl` extension in a correct way ?