简单的XML Xpath查询问题

Question

Completely new to using simple XML library in PHP, and have been using the w3 xpath syntax for assistance.

I have an xml file that looks roughly like this:

<Xml_Configs>
<Foo_Module>
   <Front_Name>a</Front_Name>
</Foo_Module>
<Bar_Module>
   <Front_Name>b</Front_Name>
</Bar_Module>
<Baz_Module>
   <Front_Name>c</Front_Name>
</Baz_Module>
</Xml_Configs>

I'm trying to figure out which module has the Front_Name of b. Right now I've only been trying to get just the attribute to match, not caring about getting the parent, and here's what I've tried:

$xmlObj->xpath('/Xml_Configs/*[@Front_Name="b"]');

That gets me nothing, however: "/Xml_Configs/*/Front_Name" does give me an array of simple xml objects with a, b, and c. And "/Xml_Configs/*/[@Front_Name="b"]" gives me invalid expression errors.

Any help you can give is appreciated, thanks!

Answer 1

I'm trying to figure out which module has the Front_Name of b

  `$xmlObj->xpath('/Xml_Configs/*[@Front_Name="b"]');` That gets me nothing 

Yes, because none of the elements that are children of the top element Xml_Configs have any attributes.

You want :

/*/*[Front_Name = 'b']

This selects all children of the top element that have a child named Font_Name with string value "b" .

XSLT - based verification :

<xsl:stylesheet version="1.0"
 xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
 <xsl:output omit-xml-declaration="yes" indent="yes"/>
 <xsl:strip-space elements="*"/>

 <xsl:template match="/">
  <xsl:copy-of select="/*/*[Front_Name = 'b']"/>
 </xsl:template>
</xsl:stylesheet>

when this transformation is applied on the provided XML document :

<Xml_Configs>
    <Foo_Module>
        <Front_Name>a</Front_Name>
    </Foo_Module>
    <Bar_Module>
        <Front_Name>b</Front_Name>
    </Bar_Module>
    <Baz_Module>
        <Front_Name>c</Front_Name>
    </Baz_Module>
</Xml_Configs>

it copies to the output the selected node :

<Bar_Module>
   <Front_Name>b</Front_Name>
</Bar_Module>

I would recommend that you obtain the XPath Visualizer -- a tool that has helped thousands of developers learn XPath while having fun at the same time.