Yaf doesn't support PHP 5.6!php
You may see this:app
Warning: PHP Startup: yaf: Unable to initialize modulethis
Module compiled with module API=20121212spa
PHP compiled with module API=20131226code
/Applications/MAMP/bin/php/php5.5.18/bin/pecl install yaform
sudo ln -s /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.10.sdk/usr/include /Applications/MAMP/bin/php/php5.5.18/includeit