Here I've got a couple of PHP libraries, one for CodeIgniter, the other a regular PHP class.
CI_Library - The CodeIgniter Library
php_class - The PHP Class
Each has a connectwise.php and a connectwise2.php. The connectwise.php file is just there for legacy reasons, you should probably use the connectwise2.php one. CW has updated their APIs several times since I initially created things.
Both work very similarly, view the appropriate README.md in the directory you are interested in.
You MUST have PHP compiled with curl support for them to work.