问如何使用PHP转换XML结构: simpleXMLElement

EN

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
    xmlns:xs="http://www.w3.org/2001/XMLSchema"
    exclude-result-prefixes="xs"
    version="1.0">

    <xsl:output indent="yes"/>
    <xsl:strip-space elements="*"/>

    <xsl:template match="product">
        <feed>
            <products>
                <product>
                    <xsl:apply-templates />
                </product>
            </products>
        </feed>
    </xsl:template>

    <xsl:template match="name|vendor">
        <xsl:copy-of select="."/>
    </xsl:template>

    <xsl:template match="propertyGroup">
        <xsl:choose>
            <xsl:when test="propertyGroupName = 'Product : Common'">
                <xsl:apply-templates select="property" mode="common"/>
            </xsl:when>
            <xsl:otherwise>
                <category><xsl:value-of select="propertyGroupName"/></category>
                <xsl:apply-templates select="property"/>
            </xsl:otherwise>
        </xsl:choose>
    </xsl:template>

    <xsl:template match="property" mode="common">
            <xsl:if test="@propertyId=2">
                <codeId><xsl:value-of select="."/></codeId>
            </xsl:if>
            <xsl:if test="@propertyId=1">
                <model><xsl:value-of select="."/></model>
            </xsl:if>
    </xsl:template>

    <xsl:template match="property">
        <xsl:element name="{@name}">
            <xsl:value-of select="value"/>
        </xsl:element>
    </xsl:template>

    <xsl:template match="file[@type='Datasheet']">
        <datasheet><xsl:value-of select="."/></datasheet>
    </xsl:template>

    <xsl:template match="image">
        <xsl:copy>
            <xsl:value-of select="."/>
        </xsl:copy>
    </xsl:template>

    <xsl:template match="*|text()"/>
</xsl:stylesheet>

<?xml version="1.0" encoding="UTF-8"?>
<feed>
   <products>
      <product>
         <name>Notebook Acer Aspire XYZ</name>
         <vendor>Acer</vendor>
         <codeId>NX.M81EX.080</codeId>
         <category>Notebook</category>
         <CPU>CPU XYZ</CPU>
         <Graphics>Graphics XYZ</Graphics>
         <RAM>RAM XYZ</RAM>
         <HDD>HDD XYZ</HDD>
         <datasheet>http://www.site.com/xyz.pdf</datasheet>
         <image>http://www.site.com/abc.jpg</image>
         <image>http://www.site.com/xyz.jpg</image>
      </product>
   </products>
</feed>

$processor = new XsltProcessor();
$xsl = new DomDocument;
$xsl->load('stylesheet.xsl');
$processor->importStylesheet($xsl);

$source = new DomDocument;
$source->load('your-xml-file.xml');

$result = $processor->transformToXML($source));