Extra content at the end of the document XML PHP RSS - php

Question

I am trying to create a RSS feed. This is the PHP code for the feed in question below.
<?xml version="1.0" encoding="utf-8" ?>
<?php
include_once 'authorization.php';
header("Content-Type: text/xml; charset=UTF-8");
$demo_id = "1";
$stmt = $mysqli->prepare("SELECT * FROM demo_files WHERE demo_id = ?");
$stmt->bind_param('i', $demo_id);
$stmt->execute();
$result = $stmt->get_result();
while($row = $result->fetch_assoc()) {
$demo_title=$row['demo_title'];
$demo_content=$row['demo_content'];
echo '<rss version="2.0">
<channel>
<title>Liorall</title>
<link>Youtube Tutorial demo</link>
<language>en-us</language>
<item>
<title>'.$post_title.'</title>
<description>'.$post_content.'</description>
</item>
</channel>
</rss>';
}
?>
Am getting this error Extra content at the end of the document
Please how can i fix it.
Thanks in Advance.

Answer 1

You're initialising $demo_title and $demo_content at the top of your loop, but emitting $post_title and $post_content later.
That will generate an undefined variable warning from PHP that will appear in your output stream and your RSS reader is likely to complain about that.
I changed that on my test system and the output now appears well-formed, but it fails the W3C Validator with some other issues you should address.