php4 will not handle *.php3 files? (potato)

["Jameson C. Burt" <jameson@monumental.com>]

Shouldn't the Debian package  php4_4.0.3pl1-0potato1.deb  
handle  *.php3  files?
Through netscape  http://localhost/test-jameson.php, 
I can see php4 working, where test-jameson.php is
   <?php phpinfo() ?>
This common test properly displays a few pages 
of PHP configuration information.

However, testing thru any of netscape/opera/mozilla 
on the file  http://localhost/test4-jameson.php3,
I only get a popup window, titled 
   Save As... (type application/x-httpd-php3)
to download the test4-jameson.php3 file.
I get this same download-response whether test4-jameson.php3 contains
the single line
   <!-- <?php phpinfo() ? -->
or the single line (recommended test line in Horde Administrator's FAQ)
   <?php php_info() ?>


Here are all lines in /etc/apache/* that contain "php", 
where all entries have been put there by Debian package installations,
1. httpd.conf:
   LoadModule php4_module /usr/lib/apache/1.3/libphp4.so

2. srm.conf:
   DirectoryIndex index.html index.php index.php3

3. mime.types:
   application/x-httpd-php                         phtml pht php
   application/x-httpd-php3                        php3
   application/x-httpd-php3-source                 phps
   application/x-httpd-php3-preprocessed           php3p



I have installed the following php and apache modules,
   Package           Version
   -------           -------
   php4              4.0.3pl1-0potato1
   php4-cgi          4.0.3pl1-0potato1
   php4-gd           4.0.3pl1-0potato1
   php4-imap         4.0.3pl1-0potato1
   php4-ldap         4.0.3pl1-0potato1
   php4-pgsql        4.0.3pl1-0potato1
   phplib            7.3dev-3.1

   apache            1.3.9-13.1
   apache-common     1.3.9-13.1
   libapache-mod-ssl 2.4.10-1.3.9-1


I presume that the php4 Debian package should handle php3 files.
I deduce this because I am installing imp, 
whose description (dpkg -s imp) includes
   Depends: php3 | php4 (>= 4.0.3pl1)
But the imp package is accessed thru the php3 web page,
   /usr/share/horde/imp/index.php3
So, while the imp package allows using the package php4 rather 
than the package php3, web access must be able 
to interpret *.php3 files---but does not.
What have I done wrong?

-- 
Jameson C. Burt, NJ9L   Fairfax, Virginia, USA
jameson@coost.com       http://www.coost.com
(202) 690-0380 (work)

You can only find truth with logic if you have already found truth without it.
-- G.K. Chesterton