[xslt] HOWTO access a node set in a variable?

["Sam Carleton" <scarleton miltonstreet com>]

I am using libxslt via PHP and in development I am using xsltproc.  In
the XSLT, I create a variable with a temporarily node set:

   <xsl:variable name="imageNodes">
     <xsl:apply-templates/>
   </xsl:variable>

With msxml transformer, to access the variable as a node set, I had to
use the msxml custom function: msxsl:node-set($imageNodes)

With xsltproc I did try to simply treat $imageNodes as a node set, but
it did not like that much.  How do I go about treating the variable as
a node set?

Sam