Allow nested xpath filter

[jwundrak]

Hi @hakre . Thanks for the library.

This PR resolves #12 . The problem is, that the current XPathFilter only check for exactly one match. If there nested matches, they are not found.

Behavior:

Using example in #12 (comment) with this script:

$xml = <<<XML
<response>
  <entry>
    <log>
      <logs count="3">
        <entry id="1">
          <baz>1</baz>
        </entry>
        <entry id="2">
          <baz>2</baz>
        </entry>
        <entry id="3">
          <baz>3</baz>
        </entry>
      </logs>
    </log>
  </entry>
</response>
XML;


$reader = XMLReader::open('data://text/plain,' . urlencode($xml));
$iterator = new XMLElementIterator($reader);
$list = new \XMLElementXpathFilter($iterator, '//entry');


/** @var \XMLReaderNode $result */
foreach($list as $item) {
    var_dump($item->getName());
    var_dump($item->getAttribute('id'));
}

Before patch

string(5) "entry"
NULL

After patch

string(5) "entry"
NULL
string(5) "entry"
string(1) "1"
string(5) "entry"
string(1) "2"
string(5) "entry"
string(1) "3"

[hakre]

@jwundrak Thanks for the fix, will be released in v0.1.12.