source: trunk/www.guidonia.net/wp/wp-admin/includes/export.php@ 44

<?php
/**
 * WordPress Export Administration API
 *
 * @package WordPress
 * @subpackage Administration
 */

/**
 * Version number for the export format.
 *
 * Bump this when something changes that might affect compatibility.
 *
 * @since unknown
 * @var string
 */
define('WXR_VERSION', '1.0');

/**
 * {@internal Missing Short Description}}
 *
 * @since unknown
 *
 * @param unknown_type $author
 */
function export_wp($author='') {
global $wpdb, $post_ids, $post;

do_action('export_wp');

$filename = 'wordpress.' . date('Y-m-d') . '.xml';

header('Content-Description: File Transfer');
header("Content-Disposition: attachment; filename=$filename");
header('Content-Type: text/xml; charset=' . get_option('blog_charset'), true);

$where = '';
if ( $author and $author != 'all' ) {
        $author_id = (int) $author;
        $where = $wpdb->prepare(" WHERE post_author = %d ", $author_id);
}

// grab a snapshot of post IDs, just in case it changes during the export
$post_ids = $wpdb->get_col("SELECT ID FROM $wpdb->posts $where ORDER BY post_date_gmt ASC");

$categories = (array) get_categories('get=all');
$tags = (array) get_tags('get=all');

/**
 * {@internal Missing Short Description}}
 *
 * @since unknown
 *
 * @param unknown_type $categories
 */
function wxr_missing_parents($categories) {
        if ( !is_array($categories) || empty($categories) )
                return array();

        foreach ( $categories as $category )
                $parents[$category->term_id] = $category->parent;

        $parents = array_unique(array_diff($parents, array_keys($parents)));

        if ( $zero = array_search('0', $parents) )
                unset($parents[$zero]);

        return $parents;
}

while ( $parents = wxr_missing_parents($categories) ) {
        $found_parents = get_categories("include=" . join(', ', $parents));
        if ( is_array($found_parents) && count($found_parents) )
                $categories = array_merge($categories, $found_parents);
        else
                break;
}

// Put them in order to be inserted with no child going before its parent
$pass = 0;
$passes = 1000 + count($categories);
while ( ( $cat = array_shift($categories) ) && ++$pass < $passes ) {
        if ( $cat->parent == 0 || isset($cats[$cat->parent]) ) {
                $cats[$cat->term_id] = $cat;
        } else {
                $categories[] = $cat;
        }
}
unset($categories);

/**
 * Place string in CDATA tag.
 *
 * @since unknown
 *
 * @param string $str String to place in XML CDATA tag.
 */
function wxr_cdata($str) {
        if ( seems_utf8($str) == false )
                $str = utf8_encode($str);

        // $str = ent2ncr(esc_html($str));

        $str = "<![CDATA[$str" . ( ( substr($str, -1) == ']' ) ? ' ' : '') . "]]>";

        return $str;
}

/**
 * {@internal Missing Short Description}}
 *
 * @since unknown
 *
 * @return string Site URL.
 */
function wxr_site_url() {
        global $current_site;

        // mu: the base url
        if ( isset($current_site->domain) ) {
                return 'http://'.$current_site->domain.$current_site->path;
        }
        // wp: the blog url
        else {
                return get_bloginfo_rss('url');
        }
}

/**
 * {@internal Missing Short Description}}
 *
 * @since unknown
 *
 * @param object $c Category Object
 */
function wxr_cat_name($c) {
        if ( empty($c->name) )
                return;

        echo '<wp:cat_name>' . wxr_cdata($c->name) . '</wp:cat_name>';
}

/**
 * {@internal Missing Short Description}}
 *
 * @since unknown
 *
 * @param object $c Category Object
 */
function wxr_category_description($c) {
        if ( empty($c->description) )
                return;

        echo '<wp:category_description>' . wxr_cdata($c->description) . '</wp:category_description>';
}

/**
 * {@internal Missing Short Description}}
 *
 * @since unknown
 *
 * @param object $t Tag Object
 */
function wxr_tag_name($t) {
        if ( empty($t->name) )
                return;

        echo '<wp:tag_name>' . wxr_cdata($t->name) . '</wp:tag_name>';
}

/**
 * {@internal Missing Short Description}}
 *
 * @since unknown
 *
 * @param object $t Tag Object
 */
function wxr_tag_description($t) {
        if ( empty($t->description) )
                return;

        echo '<wp:tag_description>' . wxr_cdata($t->description) . '</wp:tag_description>';
}

/**
 * {@internal Missing Short Description}}
 *
 * @since unknown
 */
function wxr_post_taxonomy() {
        $categories = get_the_category();
        $tags = get_the_tags();
        $the_list = '';
        $filter = 'rss';

        if ( !empty($categories) ) foreach ( (array) $categories as $category ) {
                $cat_name = sanitize_term_field('name', $category->name, $category->term_id, 'category', $filter);
                // for backwards compatibility
                $the_list .= "\n\t\t<category><![CDATA[$cat_name]]></category>\n";
                // forwards compatibility: use a unique identifier for each cat to avoid clashes
                // http://trac.wordpress.org/ticket/5447
                $the_list .= "\n\t\t<category domain=\"category\" nicename=\"{$category->slug}\"><![CDATA[$cat_name]]></category>\n";
        }

        if ( !empty($tags) ) foreach ( (array) $tags as $tag ) {
                $tag_name = sanitize_term_field('name', $tag->name, $tag->term_id, 'post_tag', $filter);
                $the_list .= "\n\t\t<category domain=\"tag\"><![CDATA[$tag_name]]></category>\n";
                // forwards compatibility as above
                $the_list .= "\n\t\t<category domain=\"tag\" nicename=\"{$tag->slug}\"><![CDATA[$tag_name]]></category>\n";
        }

        echo $the_list;
}

echo '<?xml version="1.0" encoding="' . get_bloginfo('charset') . '"?' . ">\n";

?>
<!-- This is a WordPress eXtended RSS file generated by WordPress as an export of your blog. -->
<!-- It contains information about your blog's posts, comments, and categories. -->
<!-- You may use this file to transfer that content from one site to another. -->
<!-- This file is not intended to serve as a complete backup of your blog. -->

<!-- To import this information into a WordPress blog follow these steps. -->
<!-- 1. Log into that blog as an administrator. -->
<!-- 2. Go to Tools: Import in the blog's admin panels (or Manage: Import in older versions of WordPress). -->
<!-- 3. Choose "WordPress" from the list. -->
<!-- 4. Upload this file using the form provided on that page. -->
<!-- 5. You will first be asked to map the authors in this export file to users -->
<!--    on the blog.  For each author, you may choose to map to an -->
<!--    existing user on the blog or to create a new user -->
<!-- 6. WordPress will then import each of the posts, comments, and categories -->
<!--    contained in this file into your blog -->

<?php the_generator('export');?>
<rss version="2.0"
        xmlns:excerpt="http://wordpress.org/export/<?php echo WXR_VERSION; ?>/excerpt/"
        xmlns:content="http://purl.org/rss/1.0/modules/content/"
        xmlns:wfw="http://wellformedweb.org/CommentAPI/"
        xmlns:dc="http://purl.org/dc/elements/1.1/"
        xmlns:wp="http://wordpress.org/export/<?php echo WXR_VERSION; ?>/"
>

<channel>
        <title><?php bloginfo_rss('name'); ?></title>
        <link><?php bloginfo_rss('url') ?></link>
        <description><?php bloginfo_rss("description") ?></description>
        <pubDate><?php echo mysql2date('D, d M Y H:i:s +0000', get_lastpostmodified('GMT'), false); ?></pubDate>
        <generator>http://wordpress.org/?v=<?php bloginfo_rss('version'); ?></generator>
        <language><?php echo get_option('rss_language'); ?></language>
        <wp:wxr_version><?php echo WXR_VERSION; ?></wp:wxr_version>
        <wp:base_site_url><?php echo wxr_site_url(); ?></wp:base_site_url>
        <wp:base_blog_url><?php bloginfo_rss('url'); ?></wp:base_blog_url>
<?php if ( $cats ) : foreach ( $cats as $c ) : ?>
        <wp:category><wp:category_nicename><?php echo $c->slug; ?></wp:category_nicename><wp:category_parent><?php echo $c->parent ? $cats[$c->parent]->name : ''; ?></wp:category_parent><?php wxr_cat_name($c); ?><?php wxr_category_description($c); ?></wp:category>
<?php endforeach; endif; ?>
<?php if ( $tags ) : foreach ( $tags as $t ) : ?>
        <wp:tag><wp:tag_slug><?php echo $t->slug; ?></wp:tag_slug><?php wxr_tag_name($t); ?><?php wxr_tag_description($t); ?></wp:tag>
<?php endforeach; endif; ?>
        <?php do_action('rss2_head'); ?>
        <?php if ($post_ids) {
                global $wp_query;
                $wp_query->in_the_loop = true;  // Fake being in the loop.
                // fetch 20 posts at a time rather than loading the entire table into memory
                while ( $next_posts = array_splice($post_ids, 0, 20) ) {
                        $where = "WHERE ID IN (".join(',', $next_posts).")";
                        $posts = $wpdb->get_results("SELECT * FROM $wpdb->posts $where ORDER BY post_date_gmt ASC");
                                foreach ($posts as $post) {
                        // Don't export revisions.  They bloat the export.
                        if ( 'revision' == $post->post_type )
                                continue;
                        setup_postdata($post); ?>
<item>
<title><?php echo apply_filters('the_title_rss', $post->post_title); ?></title>
<link><?php the_permalink_rss() ?></link>
<pubDate><?php echo mysql2date('D, d M Y H:i:s +0000', get_post_time('Y-m-d H:i:s', true), false); ?></pubDate>
<dc:creator><?php echo wxr_cdata(get_the_author()); ?></dc:creator>
<?php wxr_post_taxonomy() ?>

<guid isPermaLink="false"><?php the_guid(); ?></guid>
<description></description>
<content:encoded><?php echo wxr_cdata( apply_filters('the_content_export', $post->post_content) ); ?></content:encoded>
<excerpt:encoded><?php echo wxr_cdata( apply_filters('the_excerpt_export', $post->post_excerpt) ); ?></excerpt:encoded>
<wp:post_id><?php echo $post->ID; ?></wp:post_id>
<wp:post_date><?php echo $post->post_date; ?></wp:post_date>
<wp:post_date_gmt><?php echo $post->post_date_gmt; ?></wp:post_date_gmt>
<wp:comment_status><?php echo $post->comment_status; ?></wp:comment_status>
<wp:ping_status><?php echo $post->ping_status; ?></wp:ping_status>
<wp:post_name><?php echo $post->post_name; ?></wp:post_name>
<wp:status><?php echo $post->post_status; ?></wp:status>
<wp:post_parent><?php echo $post->post_parent; ?></wp:post_parent>
<wp:menu_order><?php echo $post->menu_order; ?></wp:menu_order>
<wp:post_type><?php echo $post->post_type; ?></wp:post_type>
<wp:post_password><?php echo $post->post_password; ?></wp:post_password>
<?php
if ($post->post_type == 'attachment') { ?>
<wp:attachment_url><?php echo wp_get_attachment_url($post->ID); ?></wp:attachment_url>
<?php } ?>
<?php
$postmeta = $wpdb->get_results( $wpdb->prepare("SELECT * FROM $wpdb->postmeta WHERE post_id = %d", $post->ID) );
if ( $postmeta ) {
?>
<?php foreach( $postmeta as $meta ) { ?>
<wp:postmeta>
<wp:meta_key><?php echo $meta->meta_key; ?></wp:meta_key>
<wp:meta_value><?Php echo $meta->meta_value; ?></wp:meta_value>
</wp:postmeta>
<?php } ?>
<?php } ?>
<?php
$comments = $wpdb->get_results( $wpdb->prepare("SELECT * FROM $wpdb->comments WHERE comment_post_ID = %d", $post->ID) );
if ( $comments ) { foreach ( $comments as $c ) { ?>
<wp:comment>
<wp:comment_id><?php echo $c->comment_ID; ?></wp:comment_id>
<wp:comment_author><?php echo wxr_cdata($c->comment_author); ?></wp:comment_author>
<wp:comment_author_email><?php echo $c->comment_author_email; ?></wp:comment_author_email>
<wp:comment_author_url><?php echo $c->comment_author_url; ?></wp:comment_author_url>
<wp:comment_author_IP><?php echo $c->comment_author_IP; ?></wp:comment_author_IP>
<wp:comment_date><?php echo $c->comment_date; ?></wp:comment_date>
<wp:comment_date_gmt><?php echo $c->comment_date_gmt; ?></wp:comment_date_gmt>
<wp:comment_content><?php echo wxr_cdata($c->comment_content) ?></wp:comment_content>
<wp:comment_approved><?php echo $c->comment_approved; ?></wp:comment_approved>
<wp:comment_type><?php echo $c->comment_type; ?></wp:comment_type>
<wp:comment_parent><?php echo $c->comment_parent; ?></wp:comment_parent>
<wp:comment_user_id><?php echo $c->user_id; ?></wp:comment_user_id>
</wp:comment>
<?php } } ?>
        </item>
<?php } } } ?>
</channel>
</rss>
<?php
}

?>