1. Download the file for OpenBSD 3.x as distributed by Zend
currently ZendOptimizer-3.2.8-openbsd3.4-i386.tar.gz
2. Untar (tar -xzf ZendOpt*), and fetch the files
where 5_1_x is the php you have installed
3. Put those file somewhere clean like
you NEED to keep the names unchanged
4. Simulate old libs (here's the magic)
type in the console the following command
5. Edit your /var/www/conf/php.ini and add the section
[Zend]
6. Test
Reboot your webserver
# apachectl stop
# apachectl start
Write down one php page containing phpinfo(); ?> and browse it !