如何只在xml和php中查询一个节点？

I have a code :

$query = '//Document/Status[. = "Posted"]';
$names = $xpath->query($query); // A list of matched elements

result

<Document>
  <Company>SEC</Company>
  <Type description="Misc Customer Invoices">CINV</Type>
  <DocumentID>CI_INV000239562</DocumentID>
  <DocumentDescription>Invoice</DocumentDescription>
  <Status>Posted</Status>
  <Owner>42570935</Owner>
  <Customer>42570935</Customer>
  <Location>42570935</Location>
  <Date>20111115</Date>
  <DueDate>20111115</DueDate>
  <OpenDate>20111115</OpenDate>
  <RequiredDate>20111115</RequiredDate>
  <TaxCode>AUS GST</TaxCode>
  <TaxType>Incl</TaxType>
  <TaxRate>10.00</TaxRate>
  <CurrencyCode>AUD</CurrencyCode>
  <SubTotal>115.00</SubTotal>
  <TotalTax>11.50</TotalTax>
  <Total>126.50</Total>
  <AmountDue>126.50</AmountDue>
  <AmountPaid>126.50</AmountPaid>
</Document>

If I want to display

  <DocumentID>CI_INV000239562</DocumentID>

only

What should I do ?

If I want more node to be displayed ? for example AmmountDue ?

$query = '//Document/Status[. = "Posted"]/../DocumentID/AmmountDue';

Is this possible or I must use another method ?

Thanks

There are few ways to do this, here is one of the example :-

$query = '//Document/Status[. = "Posted"]/../DocumentID';
...
$names = $xpath->query($query);
foreach ($names as $name)
{
  $node = $name->nodeValue; // string of "CI_INV000239562"
}

To seek for multiple node name :-

//Document/Status[. = "Posted"]/../*[self::DocumentID or self::AmountDue]

$query = '//Document/Status[. = "Posted"]/DocumentID';