使用XmlReader解析子节点

Question

I parsing a large XML document and am having a lt of trouble when it comes to parsing child nodes. Below is a sample of what i'm trying to parse.

<link rel="http://xxxxx/people.employees" title="employees">
    <people>
      <link href="/154" rel="http://catalog/person" title="Guy Nom" />
      <link href="/385" rel="http://catalog/person" title="Carrie Jin" />
      <link href="/162" rel="http://catalog/person" title="Joe Zee" />
      <link href="/2125" rel="http://catalog/person" title="Mark Polin" />
      <link href="/9293" rel="http://catalog/person" title="Stephen Castor" />
      <link href="/21822" rel="http://catalog/person" title="Callum Tinge" />
      <link href="/2022" rel="http://catalog/person" title="Brian Lennon" />
      <link href="/2040" rel="http://catalog/person" title="Jorja Fox" />
      <link href="/2046" rel="http://catalog/person" title="Harry Harris" />
      <link href="/2399" rel="http://catalog/person" title="Sam Muellerleile" />
    </people>
  </link>
  <link rel="http://xxxxx/people/others" title="others">
    <people>
      <link href="/7143" rel="http://catalog/person" title="James Smith" />
    </people>
  </link>

I need to differentiate between 'employees' and 'others' and store them in a separate fields. I want to do something like below:

if($xmlReader->localName == 'link') {
    if ($xmlReader->getAttribute('title') == "employees"){
      //GO TO NEXT LINK TAG AND GET NAME
      $myObject->employees[$myObject->employees_count]['name'] = $xmlReader->getAttribute('title');
      $myObject->employees_count++;

    } else if ($xmlReader->getAttribute('title') == "others"){
      //GO TO NEXT LINK TAG AND GET NAME
      $myObject->others[$myObject->others_count]['name'] = $xmlReader->getAttribute('title');
      $myObject->others_count++;

    }
  }

Obviously the bits that are commented above are the problem for me. I don't know how to read these child elements and, in my opinion, the PHP docs on this aren't great at all. I'd appreciate any help.

Answer 1

For XmlReader you can make use of the $depth property. The <link> element will like have 1 (one) so while you go on reading, you can check if the current element is still a child of that, because you will see a END_ELEMENT with the same $depth and then you know children are all consumed.

In an answer yesterday I showed how to encapsulate that logic by extending from XML_Reader:

• Why is this xmlreader code not working?

It allows to pass the depth of the parent element to a new method called readToNextChildElement($depth) that will allow you to traverse child elements only.

Usage Example:

$depth = $reader->depth; # parent elements depth
while ($reader->readToNextChildElement($depth)) {
    # only children
}

The implementation is:

class MyXMLReader extends XMLReader
{
    ...

    public function readToNextChildElement($depth)
    {
        // if the current element is the parent and
        // empty there are no children to go into
        if ($this->depth == $depth && $this->isEmptyElement) {
            return false;
        }

        while ($result = $this->read()) {
            if ($this->depth <= $depth) return false;
            if ($this->nodeType === self::ELEMENT) break;
        }

        return $result;
    }

    ...

You can find the rest of the code in the linked answer. Depending on your needs this might be helpful - if you want this XML_Reader based. Otherwise if you can load the whole document into memory instead, Xpath is much more easy to use to query your elements.

$employees_names = array_map(
    'strval', 
    $sxml->xpath('//link[@title="employees"]//link/@title')
);

That was SimpleXML.