module_load_include($type, $module, $name = NULL)
Loads a module include file.
Examples:
// Load node.admin.inc from the node module.
module_load_include('inc', 'node', 'node.admin');
// Load content_types.inc from the node module.
module_load_include('inc', 'node', 'content_types');
Do not use this function to load an install file, use module_load_install() instead. Do not use this function in a global context since it requires Drupal to be fully bootstrapped, use require_once DRUPAL