Accessing XML node value using SimpleXML and xpath

Question

There's lots of these questions, so forgive me. I've read them all.

I have the following XML document using the namespace http://www.columbasystems.com/cpng/xmlviewer/cal/1-0/ : http://events.manchester.ac.uk/f3vf/calendar/tag:manchester_museum/view:list/p:q_details/calml.xml

I'm attempting to parse this document using SimpleXML. The example code below is an attempt at accessing the value of the title node "Discovery Center" from the below.

<ns:calendar xmlns:ns="http://www.columbasystems.com/cpng/xmlviewer/cal/1-0/">
    <ns:listView>
    <ns:day date="2015-07-08" weekDay="Wed">
    <ns:event>
    <ns:id xmlns:even="http://www.columbasystems.com/customers/uom/gpp/eventid/" query="{http://www.columbasystems.com/customers/uom/gpp/eventid/}b9v-ib270yqf-nmn54k">even:b9v-ib270yqf-nmn54k</ns:id>
    <ns:title>Discovery Centre</ns:title>
    ...
</ns:event>
</ns:day>
</ns:listView>
</ns:calendar>

PHP :

$feed_uri = 'http://events.manchester.ac.uk/f3vf/calendar/tag:manchester_museum/view:list/p:q_details/calml.xml';
$xml = simplexml_load_file($feed_uri);
$xml->registerXPathNamespace("ns", "http://www.columbasystems.com/cpng/xmlviewer/cal/1-0/");

foreach($xml->xpath('//ns:calendar/ns:listView/ns:day') as $day) {
    $events = $day->xpath('//ns:event');
    foreach($events as $event) {
        var_export($event->xpath('//ns:title'));
    }
}

OUTPUTS several empty arrays:

array ( 0 => SimpleXMLElement::__set_state(array( )),

I think i'm using xpath wrong, how do i get to the values of nodes like these?

Answer 1

Your output is not an empty array. An empty array looks like this:

array()

But you have this:

array ( 0 => SimpleXMLElement::__set_state(array( )),

So, clearly the XPath is working, and giving you a list (array) of results (SimpleXMLElement objects).

The problem is that var_export isn't very good at inspecting SimpleXMLElement objects, so you can't see what result you actually got.

To get at the text content of a node, you have to cast it to a string - explicitly with (string)$node, or implicitly with something like echo. So the below will work:

foreach($xml->xpath('//ns:calendar/ns:listView/ns:day') as $day) {
    $events = $day->xpath('//ns:event');
    foreach($events as $event) {
        foreach ($event->xpath('//ns:title') as $title ) {
            echo $title;
        }
    }
}

However, you do have a small bug in your XPath expressions (irrelevant of if you used SimpleXML or any other API): the // prefix always starts at the root of the document, not the element being used as context. To search for "any depth within the current element" you need .//, e.g. $day->xpath('.//ns:event').

That said, you don't actually need anything as fancy as XPath here at all, because it's not that deep a structure. So you can just use SimpleXML's normal access methods, as long as you first select the right namespace using the ->children() method:

$cal_items = $xml->children("http://www.columbasystems.com/cpng/xmlviewer/cal/1-0/");

foreach($cal_items->listView->day as $day) {
    foreach($day->event as $event) {
        echo $event->title;
    }
}

Note that your XML contains attributes without namespace prefixes like <ns:day date="2015-07-09" weekDay="Thu">; somewhat unintuitively, these are officially in no namespace at all, so you have to switch back to the null namespace to access them:

echo $day->attributes(null)['date'];

Answer 2

I placed xml in string, change back to file. I hope, other is clear

$str = '<ns:calendar xmlns:ns="http://www.columbasystems.com/cpng/xmlviewer/cal/1-0/">
    <ns:listView>
    <ns:day date="2015-07-08" weekDay="Wed">
    <ns:event>
    <ns:id xmlns:even="http://www.columbasystems.com/customers/uom/gpp/eventid/" query="{http://www.columbasystems.com/customers/uom/gpp/eventid/}b9v-ib270yqf-nmn54k">even:b9v-ib270yqf-nmn54k</ns:id>
    <ns:title>Discovery Centre</ns:title>
</ns:event>
</ns:day>
</ns:listView>
</ns:calendar>';

$xml = simplexml_load_string($str);
$xml->registerXPathNamespace("ns", "http://www.columbasystems.com/cpng/xmlviewer/cal/1-0/");

foreach($xml->xpath('//ns:calendar/ns:listView/ns:day') as $day) {
    echo $day['date'] . ' ';
    $events = $day->xpath('.//ns:event');
    foreach($events as $event) {
        echo $event->xpath('.//ns:title/text()')[0];

    }
}

result

2015-07-08 Discovery Centre

UPDATE You can use prefix insead full url. And take in mind how get attrbute value in this case

$cal_items = $xml->children("ns",true);
foreach($cal_items->listView->day as $day) {
    echo $day->attributes()['date'] . ' ' ;
    foreach($day->event as $event) {
        echo $event->title;
    }
}