Having trouble getting the right idea - php

Question

well i'm writing a php code to edit tags and data inside those tags but i'm having big trouble getting my head around the thing.
basically i have an xml file similar to this but bigger
<users>
<user1>
<password></password>
</user1>
</users>
and the php code i'm using to try and change the user1 tag is this
function mod_user() {
// Get global Variables
global $access_level;
// Pull the data from the form
$entered_new_username = $_POST['mod_user_new_username'];
$entered_pass = $_POST['mod_user_new_password'];
$entered_confirm_pass = $_POST['mod_user_confirm_new_password'];
$entered_new_roll = $_POST['mod_user_new_roll'];
$entered_new_access_level = $_POST['mod_user_new_access_level'];
// Grab the old username from the last page as well so we know who we are looking for
$current_username = $_POST['mod_user_old_username'];
// !!-------- First thing is first. we need to run checks to make sure that this operation can be completed ----------------!!
// Check to see if the user exist. we just use the normal phaser since we are only reading and it's much easier to make loop through
$xml = simplexml_load_file('../users/users.xml');
// read the xml file find the user to be modified
foreach ($xml->children() as $xml_user_get)
{
$xml_user = ($xml_user_get->getName());
if ($xml_user == $entered_new_username){
// Set array to send data back
//$a = array ("error"=>103, "entered_user"=>$new_user, "entered_roll"=>$new_roll, "entered_access"=>$new_access_level);
// Add to session to be sent back to other page
// $_SESSION['add_error'] = $a;
die("Username Already exist - Pass");
// header('location: ../admin.php?page=usermanage&task=adduser');
}
}
// Check the passwords and make sure they match
if ($entered_pass == $entered_confirm_pass) {
// Encrypt the new password and unset the old password variables so they don't stay in memory un-encrytped
$new_password = hash('sha512', $entered_pass);
unset ($entered_pass, $entered_confirm_pass, $_POST['mod_user_new_password'], $_POST['mod_user_confirm_pass']);
}
else {
die("passwords did not match - Pass");
}
if ($entered_new_access_level != "") {
if ($entered_new_access_level < $access_level){
die("Access level is not sufficiant to grant access - Pass");
}
}
// Now to load up the xml file and commit changes.
$doc = new DOMDocument;
$doc->formatOutput = true;
$doc->perserveWhiteSpace = false;
$doc->load('../users/users.xml');
$old_user = $doc->getElementsByTagName('users')->item(0)->getElementsByTagName($current_username)->item(0);
// For initial debugging - to be deleted
if ($old_user == $current_username)
echo "old username found and matches";
// Check the variables to see if there is something to change in the data.
if ($entered_new_username != "") {
$xml_old_user = $doc->getElementsByTagName('users')->item(0)->getElementsByTagName($current_username)->item(0)->replaceChild($entered_new_username, $old_user);
echo "Username is now: " . $current_username;
}
if ($new_pass != "") {
$current_password = $doc->getElementsByTagName($current_user)->item(0)->getElementsByTagName('password')->item(0)->nodeValue;
//$replace_password = $doc
}
}
when run with just the username entered for change i get this error
Catchable fatal error: Argument 1 passed to DOMNode::replaceChild() must be an instance of DOMNode, string given, called in E:\xampp\htdocs\CGS-Intranet\admin\html\useraction.php on line 252 and defined in E:\xampp\htdocs\CGS-Intranet\admin\html\useraction.php on line 201
could someone explain to me how to do this or show me how they'd do it.. it might make a little sense to me to see how it's done :s
thanks

Answer 1

$entered_new_username is a string so you'll need to wrap it with a DOM object, via something like$doc->createElement()
$xml_old_user = $doc->getElementsByTagName('users')->item(0)->getElementsByTagName($current_username)->item(0)->replaceChild($doc->createElement($entered_new_username), $old_user);
This may not be quite right, but hopefully it points you in the correct direction.

Answer 2

alright got it writing and replacing the node that i want but i have ran into other issues i have to work out (IE: it's replacing the whole tree rather then just changing the node name)
anyway the code i used is
// For initial debugging - to be deleted
if ($old_user == $current_username)
echo "old username found and matches";
// Check the variables to see if there is something to change in the data.
if ($entered_new_username != "") {
try {
$new_node_name = $doc->createElement($entered_new_username);
$old_user->parentNode->replaceChild($new_node_name, $old_user);
}
catch (DOMException $e) {
echo $e;
}
echo "Username is now: " . $current_username;
}
if ($new_pass != "") {
$current_password = $doc->getElementsByTagName($current_user)->item(0)->getElementsByTagName('password')->item(0)->nodeValue;
//$replace_password = $doc
}
$doc->save('../users/users.xml');