DOM or DOM XML ?

I'm currently compiling (at the ./configure step at the moment) 5.03 on Redhat 9 and ran into something that confused me. I got the error message included below. [root@****]# ./configure --with-apxs2=/usr/local/apache2/bin/apxs --with-gd --with-mysql=/usr/local/mysql41 --with-mysqli=/usr/local/mysql41/bin/mysql_config . . . Configuring extensions checking whether to enable LIBXML support... yes checking libxml2 install dir... no configure: error: xml2-config not found. Please check your libxml2 installation. That, in itself, isn't too confusing, it's looking for something that's not there. Simple. I've been trying to figure out a few things though, and could use outside help: 1) Why is it trying to enable LIBXML support? 2) Which extension is it trying to load? DOM? DOM XML? Something else? Upon review I think I'd like to compile in DOM, but the manual ( http://www.php.net/dom ) doesn't mention anything about how to compile it in. Thanks, Chris