PHP - "Duplicate" the value of the addchild function

Question

I'm using PHP with SimpleXML.

It's a bit hard to explain but I was wondering how I could do the following.

I'm checking with the following code if the first parent node exists and if it doesn't exist, I create that node.

 if (!isset($xml->$serialize)){
    $set = $xml->addChild($serialize);
    }
$last = $set;

The same applies for the other nodes which are checked like that:

if (!isset($last->$serialize)){
    $set = $last->addChild($serialize);
}
$last = $set;

If the whole path isn't created yet, it works perfectly fine but if some nodes are already created then it bugs out and creates a weird path. I know why it does that but I have no idea how I should fix it.

The variable $set gets its value from creating a child node and if there is one already created then the code in "if" doesn't run and $set doesn't get a value. How can I do it so even if there is already a child node, the variable $set gets its value? Or how can I "duplicate" the value that you get from the addchild function?

EDIT: I call the xml with the following code:

$xml = new SimpleXMLElement("<permissions></permissions>");

And save it at the end of the application:

$xml->saveXML("/home/atakan/PhpstormProjects/User_Permissions/test.xml");

The output I expect looks like this. I have four variables for example:

• a/b/c/d
• a/b/c/e
• a/b/f
• g/h

Then the Xml-Output should be like in this picture.

Answer 1

You needed to break down the string into it's individual components and go through adding them one at a time. The code is mostly there, but trying to add it in all in one go isn't going to work.

I've written it as a function and you can see how it splits the input down by explode and the /. It then checks each level as it goes adding in any missing elements, or if they exist - just adjusting $set to point to the new existing element in the structure.

<?php
error_reporting ( E_ALL );
ini_set ( 'display_errors', 1 );

function addElement ( SimpleXMLElement $start, string $path )    {
    $parts = explode("/", $path);
    $set = $start;
    foreach ( $parts as $part ) {
        if ( !isset($set->$part) )  {
            $set = $set->addChild($part);
        }
        else    {
            $set = $set->$part;
        }
    }

}

$xml = new SimpleXMLElement("<permissions></permissions>");
addElement( $xml, "a/b/c/d" );
addElement( $xml, "a/b/c/e" );
addElement( $xml, "a/b/f" );
addElement( $xml, "g/h" );
echo $xml->saveXML();

Echos out...

<?xml version="1.0"?>
<permissions>
    <a>
        <b>
            <c>
                <d />
                <e />
            </c>
            <f />
        </b>
    </a>
    <g>
        <h />
    </g>
</permissions>