PHP transformToXml funktioniert nicht mehr. Debugging-Tips

[ThomasM]

Nachtrag der aufgeräumten Struktur (hier mit der kleiner-Abfrage):

<?xml version="1.0" encoding="UTF-8"?>  
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">  
  
  <xsl:output method="xml" version="1.0" encoding="UTF-8" indent="yes"/>  
  
  <xsl:variable name="refdate" select="/gigs/refdate"/>  
  
  <xsl:template match="gigs">  
    <gigs>  
      <xsl:apply-templates select="gig">  
        <xsl:sort data-type="number" select="substring(date,7,4)"/>  
        <xsl:sort data-type="number" select="substring(date,4,2)"/>  
        <xsl:sort data-type="number" select="substring(date,1,2)"/>  
      </xsl:apply-templates>  
    </gigs>  
  </xsl:template>  
  
  <xsl:template match="gig">  
    <xsl:variable name="isodate"  
                  select="concat(substring(date,7,4),substring(date,4,2),substring(date,1,2))"/>  
    <xsl:if test="$isodate &lt; $refdate">  
      <gig>  
        <title><xsl:value-of select="title"/></title>  
        <id><xsl:value-of select="id"/></id>  
        <imgurl><xsl:value-of select="imgurl"/></imgurl>  
        <date><xsl:value-of select="date"/></date>  
        <time><xsl:value-of select="time"/></time>  
        <where><xsl:value-of select="where"/></where>  
        <privat><xsl:value-of select="privat"/></privat>  
        <hp><xsl:value-of select="hp"/></hp>  
      </gig>  
    </xsl:if>  
  </xsl:template>  
  
</xsl:stylesheet>

Grüße,
Thomas