Como Ativar o mcrypt no php.ini

Sou iniciante em CakePHP e estou apanhando para ativar o mcrypt no php.ini. sou usuário de macbook.
Grato pela atenção de todos que puderem contribuir.

--
Like Us on FaceBook https://www.facebook.com/CakePHP
Find us on Twitter http://twitter.com/CakePHP

---
You received this message because you are subscribed to the Google Groups "CakePHP" group.
To unsubscribe from this group and stop receiving emails from it, send an email to cake-php+unsubscribe@googlegroups.com.
To post to this group, send email to cake-php@googlegroups.com.
Visit this group at http://groups.google.com/group/cake-php.
For more options, visit https://groups.google.com/d/optout.