php4 default package doesnt imap

[Alexander Portwein <m0shpitone@gmx.de>]

I have a Debian Woody 2.4 kernel box, that uses the default packages
for php4 and cyrus-imap. Now, when I try to call a script like the 
following:

<?
$mbox = imap_open ("{localhost:143}INBOX", "user_id", "password");
?>

I get a message that says:

Fatal error: Call to undefined function: imap_open() in 
/var/www/keyboardsamurais.de/html/imap.php on line 2

I supposed it had something to do with imap support in php4, but when I
call phpinfo() I see the required value '--with-imap=shared,/usr' in the
"Configure Command" list. So, what am I supposed to do, to get imap 
support working anyway?

Regards,
Alex