Why is this variable variable not acting properly? PHP - php

Question

I have this foreach loop.
$i2 looks like this (everytime):
$i2 = array(
'id' => "category['id']"
);
And here is a foreach loop.
foreach ($i2 as $o3 => $i3)
{
if (is_array($i3) !== true)
{
$new .= "<{$o3}>{$node->$i3}</{$o3}>";
} else {
$new .= "<{$o3}>";
$new .= "</{$o3}>";
}
}
}
$node is a new SimpleXMLElement($xml_reader->readOuterXML());. But this is working properly.
The problem is here: if I use $node->$i3 in order to get XML value of that field - it doesn't work. But if I substitute it for $node->category['id'] it does. Which seems weird as $i3 contains category['id'] and I can check that with debug tools.
I was using this in the previous projects and variable of variable was working fine. Now it doesn't. Why?
#edit
This is what happens before the code:
// i move the cursor to the first product tag
while ($xml_reader->read() and $xml_reader->name !== 'product');
// i iterate over it as long as I am inside of it
while ($xml_reader->name === 'product')
{
// i use SimpleXML inside XMLReader to work with nodes easily but without the need of loading the whole file to memory
$node = new SimpleXMLElement($xml_reader->readOuterXML());
foreach ($this->columns as $out => $in) // for each XML tag inside the product tag
{
// ... do stuff
Basically this is what happens before the code in question. The $columns is an array that enables the configuration of input XML file (keys are Prestashops XML tags and values are names of tags in the user's XML file).
For example:
<product>
<associations>
<categories>
<category>
<id></id>
</category>
<category>
</associations>
</products>
And in input one:
<category id="1"></category>
So in $columns:
$columns = ('associations' => array(
'categories' => array(
'category' => 'category['id'] // this is what $i3 later is
)
));
I can get to the given point of XML file easily. I get the category['id'] value and this is what $i3 is.

Answer 1

The PHP preprocessor tries to find the $i3 property on $node. But the object $node has no such property, and then it fails.
Are you sure you use the same syntax when trying to reach the category['id'] property in your previous projects?
You can try this syntax:
foreach ($i2 as $o3 => $i3)
{
if (is_array($i3) !== true)
{
$new .= "<{$o3}>" . eval("return \$node->$i3;") ."</{$o3}>";
} else {
$new .= "<{$o3}>";
$new .= "</{$o3}>";
}
}