I have a PHP script that caches a remote XML file. I want to XSL transform it before caching, but don't know how to do this:

<?php

   // Set this to your link Id

   $linkId = "0oiy8Plr697u3puyJy9VTUWfPrCEvEgJR";

   // Set this to a directory that has write permissions

   // for this script

   $cacheDir = "temp/";

   $cachetime = 15 * 60; // 15 minutes

   // Do not change anything below this line

   // unless you are absolutely sure

   $feedUrl="http://mydomain.com/messageService/guestlinkservlet?glId=";

   $cachefile = $cacheDir .$linkId.".xml";

   header('Content-type: text/xml');

   // Send from the cache if $cachetime is not exceeded

   if (file_exists($cachefile) && (time() - $cachetime

      < filemtime($cachefile)))

   {

      include($cachefile);
      echo "<!-- Cached ".date('jS F Y H:i', filemtime($cachefile))." -->\n";
      exit;

   }

   $contents = file_get_contents($feedUrl . $linkId);

   // show the contents of the XML file

   echo $contents;

   // write it to the cache

   $fp = fopen($cachefile, 'w');

   fwrite($fp, $contents);

   fclose($fp);

?>

This is the XSL string I want to use to transform it:

<xsl:template match="/">
    <kml xmlns="http://www.opengis.net/kml/2.2">
        <Document>
            <xsl:apply-templates select="messageList" />
        </Document>
    </kml>
</xsl:template>

<xsl:template match="messageList">
    <name>My Generated KML</name>
    <xsl:apply-templates select="message" />
</xsl:template>

<xsl:template match="message">
    <Placemark>
        <name><xsl:value-of select="esnName" /></name>
        <Point>
            <coordinates>
                <xsl:value-of select="latitude" />,<xsl:value-of select="longitude" />
            </coordinates>
        </Point>
    </Placemark>
</xsl:template>

I want to actually transform XML input and save/return a KML format. Can someone please help adjust this script? This was given to me and I am a little new to it.