Funny tests with xPath axes

test.php

<?php

/**
 * http://habrahabr.ru/post/52680/
 * http://stackoverflow.com/questions/453191/select-first-instance-only-with-xpath/
 */
$doc = new DomDocument('UTF-8', '1.0');
$doc->load(__DIR__ . '/xml.xml');

$path = new DomXPath($doc);

// Tests
echo "1: '/html/td/td[1]/a'", PHP_EOL;
$result = $path->query('/html/td/td[1]/a');
echo '  ', (int) (3 == $result->length), PHP_EOL;
echo '  ', (int) ('td1link1' == $result->item(0)->textContent), PHP_EOL;
echo '  ', (int) ('td1link2' == $result->item(1)->textContent), PHP_EOL;
echo '  ', (int) ('link2' == $result->item(2)->textContent), PHP_EOL;

echo "2: '/html/td/td[3]/a'", PHP_EOL;
$result = $path->query('/html/td/td[3]/a');
echo '  ', (int) (2 == $result->length), PHP_EOL;
echo '  ', (int) ('td3link1' == $result->item(0)->textContent), PHP_EOL;
echo '  ', (int) ('link4' == $result->item(1)->textContent), PHP_EOL;

echo "3: '/html/td/td[3]/descendant::a'", PHP_EOL;
$result = $path->query('/html/td/td[3]/descendant::a');
echo '  ', (int) (8 == $result->length), PHP_EOL;
echo '  ', (int) ('td3link1' == $result->item(0)->textContent), PHP_EOL;
echo '  ', (int) ('td31link1' == $result->item(1)->textContent), PHP_EOL;
echo '  ', (int) ('td31link2' == $result->item(2)->textContent), PHP_EOL;
echo '  ', (int) ('td32link1' == $result->item(3)->textContent), PHP_EOL;
echo '  ', (int) ('td32link2' == $result->item(4)->textContent), PHP_EOL;
echo '  ', (int) ('td33link1' == $result->item(5)->textContent), PHP_EOL;
echo '  ', (int) ('td33link2' == $result->item(6)->textContent), PHP_EOL;
echo '  ', (int) ('link4' == $result->item(7)->textContent), PHP_EOL;

echo "4: '/html/td/descendant-or-self::td[1]/a'", PHP_EOL;
$result = $path->query('/html/td/descendant-or-self::td[1]/a');
echo '  ', (int) (2 == $result->length), PHP_EOL;
echo '  ', (int) ('link0' == $result->item(0)->textContent), PHP_EOL;
echo '  ', (int) ('link1' == $result->item(1)->textContent), PHP_EOL;

echo "5: '/html/td/descendant-or-self::td[3]/a'", PHP_EOL;
$result = $path->query('/html/td/descendant-or-self::td[3]/a');
echo '  ', (int) (3 == $result->length), PHP_EOL;
echo '  ', (int) ('td2link1' == $result->item(0)->textContent), PHP_EOL;
echo '  ', (int) ('td2link2' == $result->item(1)->textContent), PHP_EOL;
echo '  ', (int) ('link3' == $result->item(2)->textContent), PHP_EOL;

echo "6: '/html/td/descendant-or-self::td[3]/descendant::a'", PHP_EOL;
$result = $path->query('/html/td/descendant-or-self::td[3]/descendant::a');
echo '  ', (int) (3 == $result->length), PHP_EOL;
echo '  ', (int) ('td2link1' == $result->item(0)->textContent), PHP_EOL;
echo '  ', (int) ('td2link2' == $result->item(1)->textContent), PHP_EOL;
echo '  ', (int) ('link3' == $result->item(2)->textContent), PHP_EOL;

echo "7: '/html/td/descendant::td[3]/a'", PHP_EOL;
$result = $path->query('/html/td/descendant::td[3]/a');
echo '  ', (int) (2 == $result->length), PHP_EOL;
echo '  ', (int) ('td3link1' == $result->item(0)->textContent), PHP_EOL;
echo '  ', (int) ('link4' == $result->item(1)->textContent), PHP_EOL;

echo "8: '/html/td/descendant::td[3]/descendant::a'", PHP_EOL;
$result = $path->query('/html/td/descendant::td[3]/descendant::a');
echo '  ', (int) (8 == $result->length), PHP_EOL;
echo '  ', (int) ('td3link1' == $result->item(0)->textContent), PHP_EOL;
echo '  ', (int) ('td31link1' == $result->item(1)->textContent), PHP_EOL;
echo '  ', (int) ('td31link2' == $result->item(2)->textContent), PHP_EOL;
echo '  ', (int) ('td32link1' == $result->item(3)->textContent), PHP_EOL;
echo '  ', (int) ('td32link2' == $result->item(4)->textContent), PHP_EOL;
echo '  ', (int) ('td33link1' == $result->item(5)->textContent), PHP_EOL;
echo '  ', (int) ('td33link2' == $result->item(6)->textContent), PHP_EOL;
echo '  ', (int) ('link4' == $result->item(7)->textContent), PHP_EOL;

echo "9: '/html/td//descendant-or-self::td[3]/a'", PHP_EOL;
$result = $path->query('/html/td//descendant-or-self::td[3]/a');
echo '  ', (int) (5 == $result->length), PHP_EOL;
echo '  ', (int) ('td2link1' == $result->item(0)->textContent), PHP_EOL;
echo '  ', (int) ('td2link2' == $result->item(1)->textContent), PHP_EOL;
echo '  ', (int) ('td32link1' == $result->item(2)->textContent), PHP_EOL;
echo '  ', (int) ('td32link2' == $result->item(3)->textContent), PHP_EOL;
echo '  ', (int) ('link3' == $result->item(4)->textContent), PHP_EOL;

echo "10: '//td[3]/a'", PHP_EOL;
$result = $path->query('//td[3]/a');
echo '  ', (int) (5 == $result->length), PHP_EOL;
echo '  ', (int) ('td3link1' == $result->item(0)->textContent), PHP_EOL;
echo '  ', (int) ('td33link1' == $result->item(1)->textContent), PHP_EOL;
echo '  ', (int) ('td33link2' == $result->item(2)->textContent), PHP_EOL;
echo '  ', (int) ('link1' == $result->item(3)->textContent), PHP_EOL;
echo '  ', (int) ('link4' == $result->item(4)->textContent), PHP_EOL;

echo "11: '//descendant::td[3]/a'", PHP_EOL;
$result = $path->query('//descendant::td[3]/a');
echo '  ', (int) (6 == $result->length), PHP_EOL;
echo '  ', (int) ('td2link1' == $result->item(0)->textContent), PHP_EOL;
echo '  ', (int) ('td2link2' == $result->item(1)->textContent), PHP_EOL;
echo '  ', (int) ('td3link1' == $result->item(2)->textContent), PHP_EOL;
echo '  ', (int) ('td33link1' == $result->item(3)->textContent), PHP_EOL;
echo '  ', (int) ('td33link2' == $result->item(4)->textContent), PHP_EOL;
echo '  ', (int) ('link4' == $result->item(5)->textContent), PHP_EOL;

echo "12: '//descendant-or-self::td[3]/descendant::a'", PHP_EOL;
$result = $path->query('//descendant-or-self::td[3]/descendant::a');
echo '  ', (int) (5 == $result->length), PHP_EOL;
echo '  ', (int) ('td2link1' == $result->item(0)->textContent), PHP_EOL;
echo '  ', (int) ('td2link2' == $result->item(1)->textContent), PHP_EOL;
echo '  ', (int) ('td32link1' == $result->item(2)->textContent), PHP_EOL;
echo '  ', (int) ('td32link2' == $result->item(3)->textContent), PHP_EOL;
echo '  ', (int) ('link3' == $result->item(4)->textContent), PHP_EOL;

echo "13: '/html/td[3]/td[1]/a[1]'", PHP_EOL;
$result = $path->query('/html/td[3]/td[1]/a[1]');
echo '  ', (int) (1 == $result->length), PHP_EOL;
echo '  ', (int) ('link2' == $result->item(0)->textContent), PHP_EOL;

echo "14: '/html/descendant-or-self::td[3]/a'", PHP_EOL;
$result = $path->query('/html/descendant-or-self::td[3]/a');
echo '  ', (int) (2 == $result->length), PHP_EOL;
echo '  ', (int) ('td2link1' == $result->item(0)->textContent), PHP_EOL;
echo '  ', (int) ('td2link2' == $result->item(1)->textContent), PHP_EOL;

echo "15: '/html/descendant-or-self::td[3]/descendant::a'", PHP_EOL;
$result = $path->query('/html/descendant-or-self::td[3]/descendant::a');
echo '  ', (int) (2 == $result->length), PHP_EOL;
echo '  ', (int) ('td2link1' == $result->item(0)->textContent), PHP_EOL;
echo '  ', (int) ('td2link2' == $result->item(1)->textContent), PHP_EOL;

echo "16: '/html/descendant::td[3]/descendant::a'", PHP_EOL;
$result = $path->query('/html/descendant::td[3]/descendant::a');
echo '  ', (int) (2 == $result->length), PHP_EOL;
echo '  ', (int) ('td2link1' == $result->item(0)->textContent), PHP_EOL;
echo '  ', (int) ('td2link2' == $result->item(1)->textContent), PHP_EOL;

echo "17: '/html/descendant-or-self::td[3]/descendant::td/a'", PHP_EOL;
$result = $path->query('/html/descendant-or-self::td[3]/descendant::td/a');
echo '  ', (int) (0 == $result->length), PHP_EOL;

echo "18: '/html/descendant-or-self::td/td/a'", PHP_EOL;
$result = $path->query('/html/descendant-or-self::*/td[3]/a');
echo '  ', (int) (5 == $result->length), PHP_EOL;
echo '  ', (int) ('td3link1' == $result->item(0)->textContent), PHP_EOL;
echo '  ', (int) ('td33link1' == $result->item(1)->textContent), PHP_EOL;
echo '  ', (int) ('td33link2' == $result->item(2)->textContent), PHP_EOL;
echo '  ', (int) ('link1' == $result->item(3)->textContent), PHP_EOL;
echo '  ', (int) ('link4' == $result->item(4)->textContent), PHP_EOL;

echo "19: '/html/td[3]/a'", PHP_EOL;
$result = $path->query('/html/td[3]/a');
echo '  ', (int) (1 == $result->length), PHP_EOL;
echo '  ', (int) ('link1' == $result->item(0)->textContent), PHP_EOL;

echo "20: '/html/descendant-or-self::td[3]/a[1]'", PHP_EOL;
$result = $path->query('/html/descendant-or-self::td[3]/a[1]');
echo '  ', (int) (1 == $result->length), PHP_EOL;
echo '  ', (int) ('td2link1' == $result->item(0)->textContent), PHP_EOL;

echo "DONE", PHP_EOL;

xml.xml

<?xml version="1.0" ?>
<html>
  <td>
    <a>link0</a>
    <td>td1 <a>td1link1</a><a>td1link2</a></td>
    <td>td2 <a>td2link1</a><a>td2link2</a></td>
    <td>td3
      <a>td3link1</a>
      <td>td31
        <a>td31link1</a>
        <a>td31link2</a>
      </td>
      <td>td32
        <a>td32link1</a>
        <a>td32link2</a>
      </td>
      <td>td33
        <a>td33link1</a>
        <a>td33link2</a>
      </td>
    </td>
  </td>
  <td> <x/></td>
  <td>
    <a>link1</a>
    <td><a>link2</a></td>
    <td><a>link3</a></td>
    <td><a>link4</a></td>
  </td>
</html>