Your php.ini contains two or more of these lines:
extension=pcntl.so
Remove all except one.
php.ini
usually lives in /etc/php.ini or /etc/php5/php.in
i. Sometimes additional .ini
files are included, you can see all of them with:
[~]% php -i | grep \.ini\$
Loaded Configuration File => /usr/local/etc/php.ini
Additional .ini files parsed => /usr/local/etc/php/extensions.ini
user_ini.filename => .user.ini => .user.ini