I have Zend Server CE 5.6 with PHP 5.2 running on Ubuntu 11.10. Now the need has arisen to run a command line PHP script that uses PHP's pnctl functionality. First of all, I had no PHP command line in my path, so I made a symlink from the Zend one: sudo ln -s /usr/local/zend/bin/php /usr/bin However, when I run my script, I now get this error: PHP Fatal error: Call to undefined function pcntl_fork() The Zend web control panel doesn't offer pnctl in the list of modules, so how do I get this functionality? Is it safe to use apt-get to install PHP directly, to run alongside the Zend instance? If so, how do I make sure I get version 5.2? I guess the following would pull in PHP 5.3: apt-get php5-cli I could probably muddle through but any pointers to help me avoid making a mess would be much appreciated!