Libvirt supports C and C++ directly, and has bindings available for other languages:
PHP: Radek Hladik develops PHP bindings.
The php-libvirt bindings also have their source online here in Github.
This allows you to easily see the code, make comments on it, create your own forks, and contribute the changes back.
Python: Libvirt comes with direct support for the Python language.
If your libvirt is installed as packages, rather than compiled by you from source code, ensure you have the appropriate package installed.
This is named libvirt-python on RHEL/Fedora, python-libvirt on Ubuntu, and may be named differently on others.
For usage information, see the Python API bindings page.
For information on using libvirt on Windows please see the Windows support page.
Support, requests or help for libvirt bindings are welcome on the mailing list, as usual try to provide enough background information and make sure you use recent version, see the help page.