For all other files, only alphanumeric characters, underscores, and the dash character ("-") are permitted. Spaces are strictly prohibited.
Any file that contains PHP code should end with the extension
".php", with the notable exception of view scripts. The
following examples show acceptable filenames for Zend Framework classes:
Zend/Db.php Zend/Controller/Front.php Zend/View/Helper/FormRadio.php
File names must map to class names as described above.