php make copies from xml files

hi im new in xml and php...i trying make an eshop with different xmls for each product..my products shows up corectly with php...i made a fuction with an add buttun and when i pressed it create a copy of each xml with the elements that i need...all products shows well as a list and the button shows in each product as well...but the problem is that each button make a copy of the first xml only(every time) and that i want is to make a copy of the xml where the button located...can someone help?ty

the xmls are 0001.xml

<product gerne="wine" 
         xmlns:xsi="http://ift.tt/ra1lAU"
         xsi:noNamespaceSchemaLocation="product.xsd">
        <id>0001</id>
        <name>krasi</name>
        <producer>someone</producer>
        <price>12.50</price>
        <category>white_wine</category>
        <img  src="images/white_wine.jpg" width="25" height="80"  />

</product

0002.xml

<product gerne="wine" 
         xmlns:xsi="http://ift.tt/ra1lAU"
         xsi:noNamespaceSchemaLocation="product.xsd">
        <id>0002</id>
        <name>Saint Cosme</name>
        <producer>Southern Rhone</producer>
        <price>20.40</price>
        <category>white_wine</category>
        <img  src="images/Saintcosme.jpg" width="25" height="80"  />

</product>

the php

<?php
    $files =glob('*.xml');
            foreach($files as $file){
                $xml=new SimpleXMLElement($file, 0, true);
                if ($xml->category=='white_wine'){

        ?>                              
    <tr>
        <td><p><?php echo $xml->id ?></p></td>
        <td><p><?php echo $xml->img->asXML() ?></p></td>

        <td><p><?php echo $xml->name ?></p></td>
        <td><p><?php echo $xml->producer ?></p></td>
        <td><p><?php echo $xml->price ?> &euro; </p></td>

        <td><form method="post" action=""><input type="submit" value="Add" name="add" /></form></td>



    </tr>  



    <?php
    include 'cProduct_function.php';


    } ?>

    <?php
    } 
    ?>

and the function

<?php 




$errors= array();
if((isset($_POST['add']))){

    $name =$xml->name;
    $producer =$xml->producer;
    $id =$xml->id;
    $price =$xml->price;
    $category =$xml->category;




    if(count($errors)== 0){

        $xml = new SimpleXMLElement('<product></product>');
        $xml->addChild('category', $category);
        $xml->addChild('id', $id);
        $xml->addChild('name', $name);
        $xml->addChild('producer', $producer);
        $xml->addChild('price', $price);


        $xml->asXML('users/' . $id . '.xml');
        header('Location: winerss.php');
        die;
        }

}
?>