PHP / XML / XSL的问题

Question

I am trying to figure out what I can do to create a code that appends data in my XML file not rewrite the XML file continuously.

I need to be able to save all the form entries and as of right now every time the form is submitted. it creates a new XML file and erases the old one.

This may be really easy to fix or I am just really dumb but I have looked at DOM syntax and do not see what I could change to change the outcome.

// define configuration file name and path
$configFile = 'abook.xml';

// if form not yet submitted
// display form
if (!isset($_POST['submit'])) {

  // set up array with default parameters
  $data = array();
  $data['name'] = null;
  $data['email'] = null;
  $data['caddress'] = null;
  $data['city'] = null;
  $data['state'] = null;
  $data['zipcode'] = null;
  $data['phone'] = null;
  $data['pug'] = null;
  $data['comment'] = null;
  $data['subscribe'] = null;

  // read current configuration values
  // use them to pre-fill the form
  if (file_exists($configFile)) {
    $doc = new DOMDocument();
    $doc->preserveWhiteSpace = false;
    $doc->load($configFile);
    $address = $doc->getElementsByTagName('address');
    foreach ($address->item(0)->childNodes as $node) {
      $data[$node->nodeName] = $node->nodeValue; 

    }        
  }

In between is a PHP form and validation code and at the end I use XML tags again:

  // generate new XML document
  $doc = new DOMDocument();

  // create and attach root element <configuration> 
  $root = $doc->createElement('addressbook');
  $configuration = $doc->appendChild($root);

  // create and attach <oven> element under <configuration>
  $address = $doc->createElement('address');
  $configuration->appendChild($address);

  // write each configuration value to the file
  foreach ($config as $key => $value) {
    if (trim($value) != '') {
      $elem = $doc->createElement($key);
      $text = $doc->createTextNode($value);
      $address->appendChild($elem);
      $elem->appendChild($text);          
    }
  }

  // format XML output



  // save XML file
  $doc->formatOutput = true;
  $doc->save($configFile) or die('ERROR: Cannot write configuration file');      
  echo 'Thank you for filling out an application.';
}  

I am really new at this so I am sorry if my code is pretty messy.

The second part I am dealing with an XSL file which I have linked to my XML file but no matter what syntax I have used to transform, nothing works to save it in a table.

Again, I don't know if this could be caused by the way I have set up my PHP to write the XML.