Ensuring X not built on FreeBSD 5.3

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Is there a method available for ensuring that xorg / xfree86 is never 
built as a dependency for any ports that could use it as a dependency? 
I'm seeing it built right now as I'm trying to build/install the 
php4-extensions port. I'm not sure what functionality requires it, but 
for future server builds I'd like to ensure I never waste time on it. Is 
there maybe something I can put in make.conf?

TIA

DS