XML Parsing Error: xml processing instruction not

Can anyone please help me?

here is my rss2.php code
<?php
if (!isset($feed)) {
$blog = 1;
$doing_rss = 1;
require('wp-blog-header.php');
}
$more = 1;
$charset = get_settings('blog_charset');
if (!$charset) $charset = 'UTF-8';
header('Content-type: text/xml', true);
?>
<?php echo '<?xml version="1.0" encoding="' . $charset . '"?'.'>'; ?>
<!-- generator="wordpress/<?php echo $wp_version ?>" -->
<rss version="2.0" xmlns:content="http://purl.org/rss/1.0/modules/content/" xmlns:wfw="http://wellformedweb.org/CommentAPI/">
<channel>
<title><?php bloginfo_rss('name') ?></title>
<link><?php bloginfo_rss('url') ?></link>
<description><?php bloginfo_rss("description") ?></description>
<copyright>Copyright <?php echo mysql2date('Y', get_lastpostdate()); ?></copyright>
<pubDate><?php echo mysql2date('D, d M Y H:i:s +0000', get_lastpostmodified('GMT'), 0); ?></pubDate>
<generator>http://wordpress.org/?v=<?php echo $wp_version ?></generator>
<?php $items_count = 0; if ($posts) { foreach ($posts as $post) { start_wp(); ?>
<item>
<title><?php the_title_rss() ?></title>
<link><?php permalink_single_rss() ?></link>
<comments><?php comments_link(); ?></comments>
<pubDate><?php echo mysql2date('D, d M Y H:i:s +0000', $post->post_date_gmt, 0); ?></pubDate>
<?php the_category_rss() ?>
<guid><?php the_permalink($id); ?></guid>
<?php if (get_settings('rss_use_excerpt')) : ?>
<description><?php the_excerpt_rss(get_settings('rss_excerpt_length'), 2) ?></description>
<?php else : ?>
<description><?php the_excerpt_rss(get_settings('rss_excerpt_length'), 2) ?></description>
<content:encoded><![CDATA[<?php the_content('', 0, '') ?>]]></content:encoded>
<?php endif; ?>
<wfw:commentRSS><?php echo comments_rss(); ?></wfw:commentRSS>
</item>
<?php $items_count++; if (($items_count == get_settings('posts_per_rss')) && empty($m)) { break; } } } ?>
</channel>
</rss>