Let's have a look at how we might benchmark and subsequently tune a PHP server. I use http_load from acme.com to do the actual testing.

This is our benchmark script
bench_include1.inc
bench_include1.inc
bench_include2.inc
menu.xml
<?xml version="1.0" encoding="ISO-8859-1"?>
<breakfast_menu>
 <food itemno="1">
  <name>Belgian Waffles</name>
  <price>$5.95</price>
  <description>two of our famous Belgian Waffles with 
               plenty of real maple syrup</description>
  <calories>650</calories>
 </food>
 <food itemno="2">
  <name>Strawberry Belgian Waffles</name>
  <price>$7.95</price>
  <description>light Belgian waffles covered with strawberries
               and whipped cream</description>
  <calories>900</calories>
 </food>
 <food itemno="3">
  <name>Berry-Berry Belgian Waffles</name>
  <price>$8.95</price>
  <description>light Belgian waffles covered with an assortment of
               fresh berries and whipped cream</description>
  <calories>900</calories>
 </food>
 <food itemno="4">
  <name>French Toast</name>
  <price>$4.50</price>
  <description>thick slices made from our homemade sourdough bread</description>
  <calories>600</calories>
 </food>
 <food itemno="5">
  <name>Homestyle Breakfast</name>
  <price>$6.95</price>
  <description>two eggs, bacon or sausage, toast, and 
               our ever-popular hash browns</description>
  <calories>950</calories>
 </food>
</breakfast_menu>
menu.xsl
<xsl:stylesheet version="1.0" 
              xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
                  xmlns="http://www.w3.org/TR/xhtml1/strict">
  <xsl:template match="/">
    <xsl:for-each select="breakfast_menu/food">
      <div style="background-color:teal;color:white;padding:4px">
        <span style="font-weight:bold;color:white">
          <xsl:value-of select="name"/>
        </span>
        - <xsl:value-of select="price"/>
      </div>
      <div style="margin-left:20px;margin-bottom:1em;font-size:10pt">
        <xsl:value-of select="description"/>
        <span style="font-style:italic">
          (<xsl:value-of select="calories"/> calories per serving)
        </span>
      </div>
    </xsl:for-each>
  </xsl:template>
</xsl:stylesheet>