Requirements

This extension requires the libxml PHP extension. This
means that passing in –enable-libxml is also required,
although this is implicitly accomplished because libxml is enabled
by default.

This extension uses an expat compat layer by default. It can use also
expat, which can be found at
» http://www.jclark.com/xml/expat.html.
The Makefile that comes with expat
does not build a library by default, you can use this make rule for
that:

libexpat.a: $(OBJS)
    ar -rc $@ $(OBJS)
    ranlib $@

A source RPM package of expat can be found at » http://sourceforge.net/projects/expat/.