How to iterate through an XML element node with dynamic children - php

Question

I currently have the following XML structure:
<root>
<maininfo>
<node>
<tournament_id>3100423</tournament_id>
<games>
<a_0>
<id>23523636</id>
<type>
<choice_4>
<choice_id>345</choice_id>
<choice_4>
<choice_9>
<choice_id>345</choice_id>
<choice_9>
... etc
</type>
</a_0>
<a_1></a_1>
<a_2></a_2>
...etc
</games>
</info>
</node>
</root>
I can easily get the id of the first node element "a_0" by just doing:
maininfo[0]->a_3130432[0]->games[0]->a_1[0]->id;
My issue is:
How do I automatically iterate (with a foreach) through all a_0, a_1, a_2 and get the values of each of these node elements and all of their children like "345" in <choice_id>345</choice_id>?
The ending numbers of a_0, a_1 + the children of choice_4, choice_9, are dynamically created and there are no logic in the _[number] counting up with +1 for each next element.

Answer 1

As it has been outlined previously on Stackoverflow (for example in Read XML dynamic PHP) and as well generally in the PHP manual (for example in Basic SimpleXML usage), you can iterate over all child elements by using foreach.
For example to go over all a_* elements, it's just
foreach ($xml->maininfo->node->games[0] as $name => $a) {
echo $name, "\n";
}
Output:
a_0
a_1
a_2
You then want to iterate over these their ->type children again. This is possible in pure PHP by putting one foreach into a another:
foreach ($xml->maininfo->node->games[0] as $name => $a) {
echo $name, "\n";
if (!$a->type[0]) {
continue;
}
foreach ($a->type[0] as $name => $choice) {
echo ' +- ', $name, "\n";
}
}
This now outputs:
a_0
+- choice_4
+- choice_9
a_1
a_2
This starts to get a bit complicated. As you can imagine since XML is famous for it's tree structures, you're not the first one running into this problem. Therefore a query-language to get elements from an XML document has been invented: Xpath.
With Xpath you can access XML data as if it was a file-system. As I know that each a_* element is a child of games and each choice_* element a child of type, it's pretty straight forward:
/*/maininfo/node/games/*/type/*
^ ^ ^
| | choice_*
root |
a_*
In PHP Simplexml this looks like:
$choices = $xml->xpath('/*/maininfo/node/games/*/type/*');
foreach ($choices as $choice) {
echo $choice->getName(), ': ', $choice->choice_id, "\n";
}
Output:
choice_4: 345
choice_9: 345
As this example shows, the data is now retrieved with a single foreach.
If you as well need access to the <a_*> elements, you need to have multiple foreach's or your own iteration but that is even a more advanced topic which I'd say would extend over the limits of your question.
I hope this is helpful so far. See as well SimpleXMLElement::children() which also gives all children (like ->games[0] in the first example). All example codes are as well available as a working, interactive online-demo.

Answer 2

If I understand it well, you can do something like:
for($i = 0; $i < $max; ++$i){
$a = $parentNode->{'a_'.$i};
}

Answer 3

You can do this very easily using SimpleXML :
<?php
$xmlStr = "<?xml version='1.0' standalone='yes'?>
<root>
<maininfo>
<node>
<tournament_id>3100423</tournament_id>
<games>
<a_0>
<id>23523636</id>
<type>
<choice_4>
<choice_id>345</choice_id>
</choice_4>
<choice_9>
<choice_id>345</choice_id>
</choice_9>
</type>
</a_0>
<a_1></a_1>
<a_2></a_2>
</games>
</node>
</maininfo>
</root>";
$xmlRoot = new SimpleXMLElement($xmlStr);
$i = 0;
foreach($xmlRoot->maininfo[0]->node[0]->games[0] as $a_x)
{
echo $i++ . " - " . htmlentities($a_x->asXML()) . "<br/>";
}
?>
I have modified some parts of your XML string to make it syntactically correct. You can view the results at http://phpfiddle.org/main/code/56q-san