PHP 递归函数如何解析 XML 文档

function parseXML($xml) {
  $parser = xml_parser_create();
  xml_set_element_handler($parser, "startElement", "endElement");
  xml_set_character_data_handler($parser, "characterData");
  xml_parse($parser, $xml);
  xml_parser_free($parser);
}

function startElement($parser, $name, $attributes) {
  echo "Start element: $name\n";
  foreach ($attributes as $key => $value) {
    echo "\tAttribute: $key='$value'\n";
  }
}

function endElement($parser, $name) {
  echo "End element: $name\n";
}

function characterData($parser, $data) {
  echo "Character data: $data\n";
}

$xml = "<root>
  <child1>This is child 1</child1>
  <child2>This is child 2
    <grandchild>This is a grandchild</grandchild>
  </child2>
  <child3>This is child 3</child3>
</root>";

parseXML($xml);

Start element: root
  Attribute: id='123'
Start element: child1
Character data: This is child 1
End element: child1
Start element: child2
Character data: This is child 2
Start element: grandchild
Character data: This is a grandchild
End element: grandchild
End element: child2
Start element: child3
Character data: This is child 3
End element: child3
End element: root