Using SimpleXML to read the last tag ID

Question

I need to append new tags to a XML file and I can achieve this by using this code:

$file = 'xml/config.xml';

$xml = simplexml_load_file($file);

$galleries = $xml->examples;

$gallery = $galleries->addChild('Example');
$gallery->addChild('ExampleID', '123');
$gallery->addChild('ExampleText', 'this is text');
$gallery->addChild('ExampleDate', '23/12/1234');

$xml->asXML($file);

My problem is the ID.
Basically I need to get the last ExampleID and increment it to the new Example tag.

How can I achieve this?

Edit

This is the XML structure:

<Examples>
    <Example>
    <ExampleID>1</ExampleID>
    <ExampleText>this is text</ExampleText>
    ...
    </Example>
    <Example>
    <ExampleID>2</ExampleID>
    <ExampleText>this is the secont text</ExampleText>
    ...
    </Example>
</Examples>

Answer 1

You can use XPath last() to find the last <Example> element, and then return the corresponding <ExampleID> child :

//Example[last()]/ExampleID

Alternatively, you can find the maximum ExampleID, as mentioned in the other answer :

//ExampleID[not(. < //ExampleID)]

---

Demo : (eval.in)

$raw = <<<XML
<Examples>
    <Example>
    <ExampleID>1</ExampleID>
    <ExampleText>this is text</ExampleText>
    ...
    </Example>
    <Example>
    <ExampleID>2</ExampleID>
    <ExampleText>this is the secont text</ExampleText>
    ...
    </Example>
</Examples>
XML;
$xml = simplexml_load_string($raw);
$lastID = (string)$xml->xpath("//Example[last()]/ExampleID")[0];
echo $lastID;

Output :

2