PHP Lib is a collection (or 'library') of interfaces, classes and functions that are required by a variety of Islandora modules, most notably the Forms modules. It is used primarily to create pages that convert records in XML formats to a more human-readable version that is also able to be easily manipulated. This is done by a series of PHP files that Drupal includes when loading these pages.
Despite being a library, php_lib is packaged as a Drupal module. It should be installed in the modules folder and enabled as a module.
See this for further information.
Further documentation for this module is available at our wiki.
Having problems or solved a problem? Check out the Islandora google groups for a solution.
If you would like to contribute to this module, please check out CONTRIBUTING.md. In addition, we have helpful Documentation for Developers info, as well as our Developers section on the Islandora.ca site.