Sharing configuration between several VHosts

Sharing configuration between several VHosts

I'm managing a httpd installation with several sites running on it, each
defined within it's own <VirtualHost> directive. There are several
configuration variables (most of them from core as well as some
php_flag/php_value) that are exactly the same for several of the sites
defined.
I would like to be able to define a configuration set that will apply to
several <VirtualHost> directives at the same time (to remove redundancy
and make the server maintenance a little bit easier).
I have considered using <Directory>, however many of the configuration
values I need to set, cannot be modified from within <Directory>. I have
also tried to define another <VirtualHost> section, containing all of the
sites I want to share the config in
<VirtualHost xx.xx.xx.xx:80 yy.yy.yy.yy:80>
...config...
</VirtualHost>
but this just results in
VirtualHost xx.xx.xx.xx:80 overlaps with VirtualHost yy.yy.yy.yy:80, the
first has precedence, perhaps you need a NameVirtualHost directive
Any idea how I can achieve this?