Manual installation on Mountain Lion (OS X 10.8)
first: Download the php source
(e.g. $ wget http://br.php.net/get/php-5.3.15.tar.gz/from/this/mirror)
nechtan$ sudo su
sh-3.2# tar -zxvf php-5.3.15.tar.gz
sh-3.2# cd php-5.3.15/ext/pcntl/
sh-3.2# phpize && ./configure && make install
sh-3.2# echo "extension=pcntl.so" >> /etc/php.ini
sh-3.2# apachectl restart
checking if everything is ok.
sh-3.2# php -m | grep pcntl
pcntl
testing pcntl with Facebook's PHP shell:
http://www.phpsh.org/