Recursively iterating through a SimpleXML object *where the structure is not known*

Question

Every example of xml iteration I've found online (including PHP docs, W3Schools, and a stackoverflow search) presumes that we know the structure ahead of time. I would like to create a loop that iterates as deep as it can go in every branch and simply returns the node names and values that it finds. For example:

<za-lord>
    <orderid>dresden1234</orderid>
    <customer>toot-toot</customer>
    <pizza>
        <sauce>marinara</sauce>
        <crust>thin</crust>
        <toppings>
            <cheese>extra</cheese>
            <veg>
                <onions>yes</onions>
                <peppers>extra</peppers>
                <olives>no</olives>
            </veg>
            <meat>
                <groundbeef>yes</groundbeef>
                <ham>no</ham>
                <sausage>no</sausage>
            </meat>
        </toppings>
    </pizza>
</za-lord>  

What I'm looking for, then, is:

orderid = dresden1234
customer = toot-toot
sauce = marinara
crust = thin
cheese = extra
onions = yes
peppers = extra
olives = no
groundbeef = yes
ham = no
sausage = no 

I've spent a couple hours now writing code examples, testing different variations on foreach, and the short version is that nothing is getting me what I want. Not knowing the structure ahead of time, is it possible to recursively iterate the xml above and return node names and values using SimpleXML, and if so, how?

Answer 1

You can use a SimpleXMLIterator object and recurse over it to get all the node values:

function list_nodes($sxi) {
    for($sxi->rewind(); $sxi->valid(); $sxi->next() ) {
        if ($sxi->hasChildren()) {
            list_nodes($sxi->current());
        }
        else {
            echo $sxi->key() . " = " . $sxi->current() . "\n";
        }
    }
}
$sxi = new SimpleXMLIterator($xmlstr);
list_nodes($sxi);

Output:

orderid = dresden1234 
customer = toot-toot 
sauce = marinara 
crust = thin 
cheese = extra 
onions = yes 
peppers = extra 
olives = no 
groundbeef = yes 
ham = no 
sausage = no

Demo on 3v4l.org

Update

If your xml can have namespaces, you have to take a more complicated approach, checking each node for children in each of the namespaces in the document:

function list_children($node, $names) {
    $children = false;
    foreach ($names as $name) {
        if (count($node->children($name))) {
            $children = true;
            foreach ($node->children($name) as $child) {
                list_children($child, $names);
            }
        }
    }
    if (!$children) {
        echo $node->getName() . " = $node\n";
    }
}

$xml = new SimpleXMLElement($xmlstr);
list_children($xml, array_merge(array(''), $xml->getNamespaces(true)));

Output (for the demo xml, same as the question but with namespaces added):

orderid = dresden1234 
customer = toot-toot 
sauce = marinara 
crust = thin 
cheese = extra 
onions = yes 
peppers = extra 
olives = no 
ham = no 
sausage = no
groundbeef = yes 

Demo on 3v4l.org