Retrieving a subset of XML nodes with PHP

Question

Using PHP, how do I get an entire subset of nodes from an XML document? I can retrieve something like:

Answer 1

The answer would be to use XPath.

$people = simplexml_load_string(
    '
    
      
        Jane Doe
        21
      
      
        John Smith
        34
      
    '
);

// get all  nodes
$people->xpath('//certain');

// get all  nodes whose  is "John Smith"
print_r($people->xpath('//certain[name = "John Smith"]'));

// get all  nodes whose  child's value is greater than 21
print_r($people->xpath('//certain[age > 21]'));

---

Take 2

So apparently you want to copy some nodes from a document into another document? SimpleXML doesn't support that. DOM has methods for that but they're kind of annoying to use. Which one are you using? Here's what I use: SimpleDOM. In fact, it's really SimpleXML augmented with DOM's methods.

include 'SimpleDOM.php';
$results = simpledom_load_string('');

foreach ($people->xpath('//certain') as $certain)
{
    $results->appendChild($certain);
}

That routine finds all node via XPath, then appends them to the new document.