Using the classname's part as path elements makes ugly paths: Mail/parser/set.php, ezcMailSmtpTransport => Mail/smtp/transport.php, ezcMailTransportOptions => Mail/transport/options.php, ezcMailAddress => Mail/mail/address.php, ]]> More logical names (mail_autoload.php): Mail/parser/interfaces/parser_set.php, ezcMailSmtpTransport => Mail/transports/smtp/transport_smtp.php, ezcMailTransportOptions => Mail/options/transport_options.php, ezcMailAddress => Mail/structs/mail_address.php, ]]> Some problems: Clashes in first part of the classname Needs installation into correct place for development