prob with PHP 4.1

I have experience with other OOP languages, but this is my first foray into classes in PHP.
(full paths replaced with ...)
I want to use class.error_handler.php, but have run into a few problems.
The first is:
Parse error: parse error, unexpected T_STRING, expecting T_OLD_FUNCTION or T_FUNCTION or T_VAR or '}' in .../class.sendmail.php on line 9
which is probably the public keyword.

removing that yields:
Warning: main(db_config.php): failed to open stream: No such file or directory .../class.sendmail.php on line 3

Warning: main(): Failed opening 'db_config.php' for inclusion (include_path='.:/usr/local/lib/php:/usr/local/lib/php/PEAR:/usr/local/share/pear') in ...class.sendmail.php on line 3

which is expected as I don't know of db_config.php.

I can easily remove the public/private keywords, but what of the db_config ?

thanks for your time

bill