PHP SimpleXML recursive function to list children and attributes - php

Question

I need some help on the SimpleXML calls for a recursive function that lists the elements name and attributes. Making a XML config file system but each script will have it's own config file as well as a new naming convention. So what I need is an easy way to map out all the elements that have attributes, so like in example 1 I need a simple way to call all the processes but I don't know how to do this without hard coding the elements name is the function call. Is there a way to recursively call a function to match a child element name? I did see the xpath functionality but I don't see how to use this for attributes.
Also does the XML in the examples look correct? can I structure my XML like this?
Example 1:
<application>
<processes>
<process id="123" name="run batch A" />
<process id="122" name="run batch B" />
<process id="129" name="run batch C" />
</processes>
<connections>
<databases>
<database usr="test" pss="test" hst="test" dbn="test" />
</databases>
<shells>
<ssh usr="test" pss="test" hst="test-2" />
<ssh usr="test" pss="test" hst="test-1" />
</shells>
</connections>
</application>
Example 2:
<config>
<queues>
<queue id="1" name="test" />
<queue id="2" name="production" />
<queue id="3" name="error" />
</queues>
</config>
Pseudo code:
// Would return matching process id
getProcess($process_id) {
return the process attributes as array that are in the XML
}
// Would return matching DBN (database name)
getDatabase($database_name) {
return the database attributes as array that are in the XML
}
// Would return matching SSH Host
getSSHHost($ssh_host) {
return the ssh attributes as array that are in the XML
}
// Would return matching SSH User
getSSHUser($ssh_user) {
return the ssh attributes as array that are in the XML
}
// Would return matching Queue
getQueue($queue_id) {
return the queue attributes as array that are in the XML
}
EDIT:
Can I pass two parms? on the first method you have suggested #Gordon
I just got it, thnx, see below
public function findProcessById($id, $name)
{
$attr = false;
$el = $this->xml->xpath("//process[#id='$id'][#name='$name']"); // How do I also filter by the name?
if($el && count($el) === 1) {
$attr = (array) $el[0]->attributes();
$attr = $attr['#attributes'];
}
return $attr;
}

Answer 1

The XML looks good to me. The only thing I wouldn't do is making name an attribute in process, because it contains spaces and should be a textnode then (in my opinion). But since SimpleXml does not complain about it, I guess it boils down to personal preference.
I'd likely approach this with a DataFinder class, encapsulating XPath queries, e.g.
class XmlFinder
{
protected $xml;
public function __construct($xml)
{
$this->xml = new SimpleXMLElement($xml);
}
public function findProcessById($id)
{
$attr = false;
$el = $this->xml->xpath("//process[#id='$id']");
if($el && count($el) === 1) {
$attr = (array) $el[0]->attributes();
$attr = $attr['#attributes'];
}
return $attr;
}
// ... other methods ...
}
and then use it with
$finder = new XmlFinder($xml);
print_r( $finder->findProcessById(122) );
Output:
Array
(
[id] => 122
[name] => run batch B
)
XPath tutorial:
http://www.w3schools.com/XPath/default.asp
An alternative would be to use SimpleXmlIterator to iterate over the elements. Iterators can be decorated with other Iterators, so you can do:
class XmlFilterIterator extends FilterIterator
{
protected $filterElement;
public function setFilterElement($name)
{
$this->filterElement = $name;
}
public function accept()
{
return ($this->current()->getName() === $this->filterElement);
}
}
$sxi = new XmlFilterIterator(
new RecursiveIteratorIterator(
new SimpleXmlIterator($xml)));
$sxi->setFilterElement('process');
foreach($sxi as $el) {
var_dump( $el ); // will only give process elements
}
You would have to add some more methods to have the filter work for attributes, but this is a rather trivial task.
Introduction to SplIterators:
http://www.phpro.org/tutorials/Introduction-to-SPL.html