The class must be either in memory (PEAR_Validate or PEAR_Validate_PECL) or be available for include_once() via a simple formula: Transform the underscores (_) into directory separators (/), append .php and include.
A validation class named Foo_Bar_Baz should be available for inclusion via this code:
<?php include_once 'Foo/Bar/Baz.php'; ?>
In addition, the validation package must be available for installation from the channel with the version number to install specified by the $version parameter.
pass in FALSE to reset to the default packagename regex
The package version that must be installed for this channel to validate properly.