通过HTML表单编辑XML（PHP）

I'm trying to create a form that will let you edit the contents of an xml tag. i currently have a form.php:

<?php
$data=simplexml_load_file('welcome.xml');
$welcome=$data->item->name;
?>

<form method="post">
    <textarea name="name"><?php echo $welcome ?></textarea>
    <br>
    <input type="submit" name="submit" value="submit">
</form>

<?php
if(isset($_POST['submit'])) {
$data=simplexml_load_file('welcome.xml');
$data->item->name=$_POST['name'];
$handle=fopen("welcome.xml","wb");
fwrite($handle,$xml->asXML());
fclose($handle);
}
?>

and welcome.xml:

<welcome>
    <item>
        <name>$welcome</name>
    </item>
</welcome>

when i press submit it doesn't save what's entered, it just refreshes the page and deletes whatever the value in the xml file was before..

UPDATE

The form works now, but I've added a reset button, i need it to clear the xml file so it only has the <welcome> tags. I've changed $data->item->name=$_POST['welcome']; to $data=''; but it deletes the text and keeps the tags still.

You can do it with simplexml.

To read data from xml:

$data = simplexml_load_file('welcome.xml');

$welcome = $data->item[0]->name;

And to write data:

$data = simplexml_load_file('welcome.xml');

$data->item[0]->name = $_POST['welcome'];

$handle = fopen("welcome.xml", "wb"); 
fwrite($handle, $xml->asXML());
fclose($handle);

EDIT: For the question in the comment:

<?php
if(isset($_POST['submit'])) {
$data=simplexml_load_file('welcome.xml');
$data->item->name=$_POST['name'];
$handle=fopen("welcome.xml","wb");
fwrite($handle,$data->asXML());
fclose($handle);
}

$data=simplexml_load_file('welcome.xml');
$welcome=$data->item->name;

?>

<form method="post">
    <textarea name="name"><?php echo $welcome ?></textarea>
    <br>
    <input type="submit" name="submit" value="submit">
</form>