How to change XML attributes (and values) with SimpleXMLElement in PHP - php

Question

I got a problem when I set a value/attribute of XML tag.
This is my PHP code:
$f=simplexml_load_file("String.xml");
$f2=$f->imgdir;
foreach($f2 as $imgdir)
{
$st=$imgdir->string;
foreach($st as $str)
{
$fd=$str->attributes();
$fd['value']='New Value';
}
}
$f->asXML("String.xml");
And this is my String.xml file's content:
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<imgdir name="Cash.img">
<imgdir name="5000011">
<string name="name" value="Monkey"/>
<string name="desc" value="A lovely effect that shows a baby angel floating around as your protector. Designate a HotKey to turn the effect on/off."/>
</imgdir>
<imgdir name="5010000">
<string name="name" value="Sunny Day"/>
<string name="desc" value="A special effect in which you&apos;ll see a brightly smiling sun floating over you. On the KeyConfig, configure this on a button of your choice to turn the effect on/off."/>
</imgdir>
</imgdir>
How can I change the value attribute of per <string> tag and save the XML file? What should I do with my current code?
Thank for reading my question!

Answer 1

Basics
I suggest you select all <string> nodes with xpath:
$xml = simplexml_load_string($x); // assume XML in $x
$strings = $xml->xpath("//string");
The above statement will select all <string> nodes as SimpleXml elements into an array.
The double slash in //string will take <string> regardless of their position in the tree.
Now it is simple to iterate over $strings and set the new value:
foreach ($strings as $string)
$string["value"] = "new value";
Note that the changes applied to $strings happen in $xml, so:
echo $xml->asXML();
will show the changes.
see it working: https://eval.in/499427
Expanded
Of course, you might want to select only certain <string> nodes, e.g. all having name="name". In this case, you can tell xpath like:
$strings = $xml->xpath("//string[#name='name']");
Note the condition set in [] and #name referring to the attribute name.