XPath解析成数组

$xml = simplexml_load_file('Request.xml');
$xml->registerXPathNamespace("ess", "localhost/ESS");
$partnums = array();

$xp = "descendant::ess:ProPartList/ess:ProPart/ess:SelectedPart";
$selected = $xml->xpath($xp);        
$x = 0;
foreach($selected as $part) {
    $partnuminfo = $part->xpath("//ess:PartNumInfo");
    foreach($partnuminfo as $p) {
        echo $p->asXML();
        $_Type = (string)$part->children("ess",true)->PartNumType;
        $partnums[$x] = array($_Type => (string)$part->children("ess",true)->PartNum);
        $x++;
    }
}
print_r($partnums);

Using the code above, I cannot seem to get my head around parsing the XML below:

<ess:ProInfo>
    <ess:ProPartList>
        <ess:ProPart>
            <ess:SelectedPart>
                <ess:PartNumInfo>
                    <ess:PartNumType>OE</ess:PartNumType>
                    <ess:PartNum>04715SNAA90ZZ</ess:PartNum>
                </ess:PartNumInfo>
                <ess:PartNumInfo>
                    <ess:PartNumType>IC</ess:PartNumType>
                    <ess:PartNum>536-01037</ess:PartNum>
                </ess:PartNumInfo>
                <ess:PartNumInfo>
                    <ess:PartNumType>PType</ess:PartNumType>
                    <ess:PartNum>536</ess:PartNum>
                </ess:PartNumInfo>
            </ess:SelectedPart>
        </ess:ProPart>
        <ess:ProPart>
            <ess:SelectedPart>
                <ess:PartNumInfo>
                    <ess:PartNumType>OE</ess:PartNumType>
                    <ess:PartNum>71570SNAA00</ess:PartNum>
                </ess:PartNumInfo>
                <ess:PartNumInfo>
                    <ess:PartNumType>IC</ess:PartNumType>
                    <ess:PartNum>536-01036</ess:PartNum>
                </ess:PartNumInfo>
            </ess:SelectedPart>
        </ess:ProPart>
        <ess:ProPart>
            <ess:SelectedPart>
                <ess:PartNumInfo>
                    <ess:PartNumType>OE</ess:PartNumType>
                    <ess:PartNum>66100SNEA00ZZ</ess:PartNum>
                </ess:PartNumInfo>
                <ess:PartNumInfo>
                    <ess:PartNumType>IC</ess:PartNumType>
                    <ess:PartNum>117-50338</ess:PartNum>
                </ess:PartNumInfo>                                
            </ess:SelectedPart>
        </ess:ProPart>
        <ess:ProPart>
            <ess:SelectedPart>
                <ess:PartNumInfo>
                    <ess:PartNumType>OE</ess:PartNumType>
                    <ess:PartNum>04655SNE305ZZ</ess:PartNum>
                </ess:PartNumInfo>
            </ess:SelectedPart>
        </ess:ProPart>
    </ess:ProPartList>
</ess:ProInfo>

And creating this array()

array(
    0 => array("OE" => "04715SNAA90ZZ", "IC" => "536-01037", "PType" => "536"),
    1 => array("OE" => "71570SNAA00",   "IC" => "536-01036"),
    2 => array("OE" => "66100SNEA00ZZ", "IC" => "117-50338"),
    3 => array("OE" => "04655SNE305ZZ")
)

I think the main problem is using //ess:PartNumInfo in the second XPath expression, this can cause other elements to be found as well (// means any element). If you change that to use the descendant:: axis as in the first XPath expression, it will only look for elements inside the start point.

I've changed the code to also group the elements at the next level, so...

$xp = "descendant::ess:ProPartList/ess:ProPart/ess:SelectedPart";
$selected = $xml->xpath($xp);
foreach($selected as $part) {
    $partnuminfo = $part->xpath("descendant::ess:PartNumInfo");
    $group = array();
    foreach($partnuminfo as $p) {
        $_Type = (string)$p->children("ess",true)->PartNumType;
        $group[$_Type] =(string)$p->children("ess",true)->PartNum;
    }
    $partnums[] = $group;
}
print_r($partnums);

gives...

Array
(
    [0] => Array
        (
            [OE] => 04715SNAA90ZZ
            [IC] => 536-01037
            [PType] => 536
        )

    [1] => Array
        (
            [OE] => 71570SNAA00
            [IC] => 536-01036
        )

    [2] => Array
        (
            [OE] => 66100SNEA00ZZ
            [IC] => 117-50338
        )

    [3] => Array
        (
            [OE] => 04655SNE305ZZ
        )

)