Zend::loadClass() loads a PHP file whose filename is formatted like
"$className.php", and then checks for the existance of the class $className.
<?php loadClass($class, $dirs) ?>
If the file is not found or the class does not exist after the load, a Zend_Exception is
thrown. Zend::loadFile() is used for loading, and the $dirs argument is
passed directly to it..
If you ask for a class with underscores in the name, and $dirs is null (the default),
Zend::loadClass() will auto-discover the $dirs from the class name
by converting underscores to directory separators. For example, if $class is
Zend_Example_Class, that will map to a path of Zend/Example/Class.php.