For Ubuntu 12.04, these are the steps:1. Install packages: gnupg libgpg-error-dev libassuan-dev2. Download GPGME library from http://www.gnupg.org/download/index.en.html#gpgme3. Extract, then run configure make && sudo make install4. Install PECL extension sudo pecl install gnupg5. Add to php.ini extension=gnupg.so