[xsl] Passing variables into XSLT via parameters ... can't get it to work

[Duncan Anker <danker@xxxxxxxxxxxxx>]

Hi List,

I have a setup where I want to store my HTML pages as XML and use XSLT 
to apply common layout features, e.g. headers and footers. I also need 
to pass dynamic data into some of the pages, and rather than process 
everything twice I (perhaps foolishly) thought I could use parameters to 
send the data in. So I have a $parameters variable which contains a 
string something like '<parameters><namespace variable1="value" 
variable2="value" /></parameters>'

In my HTML fragments where I want to place a variable, I use a call-out like

<variable name="namespace:variable1" />

Then in my XSLT I have this:
<xsl:template match="variable">
 <xsl:variable name="a" select="substring-before(@name, ':')" />
 <xsl:variable name="b" select="substring-after(@name, ':')" />
   <xsl:value-of select="exslt:node-set($parameters)//*[name() = 
$a]/@*[name() = $b]" />
</xsl:template>

[As an aside, I couldn't get the substring-before and -after to work 
directly in the XPath expression. Am I missing something, or do they 
need to be assigned to variables like that to be used?]

This all seems to work well enough when the $parameters string is set 
inside the stylesheet, however when I try to pass it in as a global 
parameter I get empty results. I know the string is making it in because 
<xsl:value-of select="$parameters" /> prints out the escaped string. 
What I can't figure out is why it is not being treated the same way as a 
local variable would be.

Can anyone shed any light on this? I've spent 2 days banging my head 
against Google so far. I am trying to do this with PHP 5.1.4 compiled 
against libXML and lbXSLT, versions 2.6.23 and 1.1.15 respectively. I'd 
like to finger PHP as the culprit, but I get the same results when 
running xsltproc over the documents.

Regards,
Duncan