New /wp-admin/includes/export.php for WordPress which generates JSON output.

export.php

<?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 2.5.0
 */
define( 'WXR_VERSION', '1.2' );

/**
 * Generates the WXR export file for download
 *
 * @since 2.1.0
 *
 * @param array $args Filters defining what should be included in the export
 */
function export_wp( $args = array() ) {
	global $wpdb, $post;

	$defaults = array( 'content' => 'all', 'author' => false, 'category' => false,
		'start_date' => false, 'end_date' => false, 'status' => false,
	);
	$args = wp_parse_args( $args, $defaults );

	do_action( 'export_wp' );

	$sitename = sanitize_key( get_bloginfo( 'name' ) );
	if ( ! empty($sitename) ) $sitename .= '.';
	$filename = $sitename . 'wordpress.' . date( 'Y-m-d' ) . '.json';

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

	if ( 'all' != $args['content'] && post_type_exists( $args['content'] ) ) {
		$ptype = get_post_type_object( $args['content'] );
		if ( ! $ptype->can_export )
			$args['content'] = 'post';

		$where = $wpdb->prepare( "{$wpdb->posts}.post_type = %s", $args['content'] );
	} else {
		$post_types = get_post_types( array( 'can_export' => true ) );
		$esses = array_fill( 0, count($post_types), '%s' );
		$where = $wpdb->prepare( "{$wpdb->posts}.post_type IN (" . implode( ',', $esses ) . ')', $post_types );
	}

	if ( $args['status'] && ( 'post' == $args['content'] || 'page' == $args['content'] ) )
		$where .= $wpdb->prepare( " AND {$wpdb->posts}.post_status = %s", $args['status'] );
	else
		$where .= " AND {$wpdb->posts}.post_status != 'auto-draft'";

	$join = '';
	if ( $args['category'] && 'post' == $args['content'] ) {
		if ( $term = term_exists( $args['category'], 'category' ) ) {
			$join = "INNER JOIN {$wpdb->term_relationships} ON ({$wpdb->posts}.ID = {$wpdb->term_relationships}.object_id)";
			$where .= $wpdb->prepare( " AND {$wpdb->term_relationships}.term_taxonomy_id = %d", $term['term_taxonomy_id'] );
		}
	}

	if ( 'post' == $args['content'] || 'page' == $args['content'] ) {
		if ( $args['author'] )
			$where .= $wpdb->prepare( " AND {$wpdb->posts}.post_author = %d", $args['author'] );

		if ( $args['start_date'] )
			$where .= $wpdb->prepare( " AND {$wpdb->posts}.post_date >= %s", date( 'Y-m-d', strtotime($args['start_date']) ) );

		if ( $args['end_date'] )
			$where .= $wpdb->prepare( " AND {$wpdb->posts}.post_date < %s", date( 'Y-m-d', strtotime('+1 month', strtotime($args['end_date'])) ) );
	}

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

	// get the requested terms ready, empty unless posts filtered by category or all content
	$cats = $tags = $terms = array();
	if ( isset( $term ) && $term ) {
		$cat = get_term( $term['term_id'], 'category' );
		$cats = array( $cat->term_id => $cat );
		unset( $term, $cat );
	} else if ( 'all' == $args['content'] ) {
		$categories = (array) get_categories( array( 'get' => 'all' ) );
		$tags = (array) get_tags( array( 'get' => 'all' ) );

		$custom_taxonomies = get_taxonomies( array( '_builtin' => false ) );
		$custom_terms = (array) get_terms( $custom_taxonomies, array( 'get' => 'all' ) );

		// put categories in order with no child going before its parent
		while ( $cat = array_shift( $categories ) ) {
			if ( $cat->parent == 0 || isset( $cats[$cat->parent] ) )
				$cats[$cat->term_id] = $cat;
			else
				$categories[] = $cat;
		}

		// put terms in order with no child going before its parent
		while ( $t = array_shift( $custom_terms ) ) {
			if ( $t->parent == 0 || isset( $terms[$t->parent] ) )
				$terms[$t->term_id] = $t;
			else
				$custom_terms[] = $t;
		}

		unset( $categories, $custom_taxonomies, $custom_terms );
	}

	/**
	 * Return the URL of the site
	 *
	 * @since 2.5.0
	 *
	 * @return string Site URL.
	 */
	function wxr_site_url() {
		// ms: the base url
		if ( is_multisite() )
			return network_home_url();
		// wp: the blog url
		else
			return get_bloginfo_rss( 'url' );
	}

	/**
	 * Output a cat_name JSON from a given category object
	 *
	 * @since 2.1.0
	 *
	 * @param object $category Category Object
	 */
	function wxr_cat_name( $category ) {
		if ( empty( $category->name ) )
			return;

//		echo '<wp:cat_name>' . wxr_cdata( $category->name ) . '</wp:cat_name>';
        echo ",\n\"wp:cat_name\": \"" . $category->name . "\"";

    }

	/**
	 * Output a category_description JSON from a given category object
	 *
	 * @since 2.1.0
	 *
	 * @param object $category Category Object
	 */
	function wxr_category_description( $category ) {
		if ( empty( $category->description ) )
			return;

		echo ",\n\"wp:category_description\": \"" . $category->description . "\"";
	}

	/**
	 * Output a tag_name JSON from a given tag object
	 *
	 * @since 2.3.0
	 *
	 * @param object $tag Tag Object
	 */
	function wxr_tag_name( $tag ) {
		if ( empty( $tag->name ) )
			return;

		echo ",\n\"wp:tag_name\": \"" . $tag->name . "\"";
	}

	/**
	 * Output a tag_description JSON from a given tag object
	 *
	 * @since 2.3.0
	 *
	 * @param object $tag Tag Object
	 */
	function wxr_tag_description( $tag ) {
		if ( empty( $tag->description ) )
			return;

		echo ',\n"wp:tag_description": "' . $tag->description . '"';
	}

	/**
	 * Output a term_name JSON from a given term object
	 *
	 * @since 2.9.0
	 *
	 * @param object $term Term Object
	 */
	function wxr_term_name( $term ) {
		if ( empty( $term->name ) )
			return;

		echo '"wp:term_name": "' . $term->name . '"';
	}

	/**
	 * Output a term_description JSON from a given term object
	 *
	 * @since 2.9.0
	 *
	 * @param object $term Term Object
	 */
	function wxr_term_description( $term ) {
		if ( empty( $term->description ) )
			return;

		echo '"wp:term_description": "' . $term->description . '"';
	}

	/**
	 * Output list of authors with posts
	 *
	 * @since 3.1.0
	 */
	function wxr_authors_list() {
		global $wpdb;
        $bs = "\x08";
		$authors = array();
		$results = $wpdb->get_results( "SELECT DISTINCT post_author FROM $wpdb->posts WHERE post_status != 'auto-draft'" );
		foreach ( (array) $results as $result )
			$authors[] = get_userdata( $result->post_author );

		$authors = array_filter( $authors );
        echo "\"wp:author\": [\n";
		foreach ( $authors as $author ) {
			echo "{\n";
			echo "\t\"wp:author_id\": \"" . $author->ID . "\",\n";
			echo "\t\"wp:author_login\": \"" . $author->user_login . "\",\n";
			echo "\t\"wp:author_email\": \"" . $author->user_email . "\",\n";
			echo "\t\"wp:author_display_name\": \"" . $author->display_name . "\",\n";
			echo "\t\"wp:author_first_name\": \"" . $author->user_firstname . "\",\n";
			echo "\t\"wp:author_last_name\": \"" . $author->user_lastname . "\"\n";
            if ($author == end($authors))
                echo "}\n";
			else
                echo "},\n";
		}
        echo "],\n";
	}

	/**
	 * Ouput all navigation menu terms
	 *
	 * @since 3.1.0
	 */
	function wxr_nav_menu_terms() {
		$nav_menus = wp_get_nav_menus();
		if ( empty( $nav_menus ) || ! is_array( $nav_menus ) )
			return;
        echo "\"wp:term\": [";
		foreach ( $nav_menus as $menu ) {
			echo "{\n\t\"wp:term_id\": \"{$menu->term_id}\",\n\t\"wp:term_taxonomy\": \"nav_menu\",\n\t\"wp:term_slug\": \"{$menu->slug}\"},\n";
			wxr_term_name( $menu );
            echo ",\n";
		}
        echo "]\n";
	}

	/**
	 * Output list of taxonomy terms, in JSON format, associated with a post
	 *
	 * @since 2.3.0
	 */
	function wxr_post_taxonomy() {
		$post = get_post();

		$taxonomies = get_object_taxonomies( $post->post_type );
		if ( empty( $taxonomies ) )
			return;
		$terms = wp_get_object_terms( $post->ID, $taxonomies );
        echo "\"category\": [\n";
		foreach ( (array) $terms as $term ) {
//			echo "\t\t<category domain=\"{$term->taxonomy}\" nicename=\"{$term->slug}\">" . wxr_cdata( $term->name ) . "</category>\n";
            echo "{\n\t\"-domain\": \"{$term->taxonomy}\",\n\t\"-nicename\": \"{$term->slug}\",\n\t\"-#cdata-section\": \"{$term->name}\"\n";
            if ($term == end($terms))
                  echo "}\n";
             else
                  echo "},\n";
		}
        echo "],\n";
	}

	function wxr_filter_postmeta( $return_me, $meta_key ) {
		if ( '_edit_lock' == $meta_key )
			$return_me = true;
		return $return_me;
	}
	add_filter( 'wxr_export_skip_postmeta', 'wxr_filter_postmeta', 10, 2 );


    echo "{\n";?>


"channel": {
    "title": "<?php bloginfo_rss( 'name' ); ?>",
    "link": "<?php bloginfo_rss( 'url' ); ?>",
    "description": "<?php bloginfo_rss( 'description' ); ?>",
    "pubDate": "<?php echo date( 'D, d M Y H:i:s +0000' ); ?>",
    "language": "<?php bloginfo_rss( 'language' ); ?>",
    "wp:wxr_version": "<?php echo WXR_VERSION; ?>",
    "wp:base_site_url": "<?php echo wxr_site_url(); ?>",
    "wp:base_blog_url": "<?php bloginfo_rss( 'url' ); ?>",

<?php wxr_authors_list(); ?>

    "wp:category": [
<?php foreach ( $cats as $c ) : ?>
        {
            "wp:term_id": "<?php echo $c->term_id ?>",
            "wp:category_nicename": "<?php echo $c->slug; ?>",
            "wp:category_parent": "<?php echo $c->parent ? $cats[$c->parent]->slug : ''; ?>"<?php wxr_cat_name( $c ); ?><?php wxr_category_description( $c ); ?>
<?php
        if ($c == end($cats))
            echo "\n}\n";
        else
            echo "\n},\n";
?>
<?php endforeach; ?>
    ],
    "wp:tag": [
<?php foreach ( $tags as $t ) : ?>
	    {
            "wp:term_id": "<?php echo $t->term_id ?>",
            "wp:tag_slug": "<?php echo $t->slug; ?>"<?php wxr_tag_name( $t ); ?><?php wxr_tag_description( $t ); ?>
<?php
        if ($t == end($tags))
            echo "\n}\n";
        else
            echo "\n},\n";
?>
<?php endforeach; ?>
    ],
    "wp:term": [
<?php foreach ( $terms as $t ) : ?>
        {
	        "wp:term_id": "<?php echo $t->term_id ?>",
            "wp:term_taxonomy": "<?php echo $t->taxonomy; ?>",
            "wp:term_slug": "<?php echo $t->slug; ?>",
            "wp:term_parent": "<?php echo $t->parent ? $terms[$t->parent]->slug : ''; ?>",
            <?php wxr_term_name( $t ); ?>,
            <?php wxr_term_description( $t ); ?>
<?php endforeach; ?>
    ],
<?php if ( 'all' == $args['content'] ) wxr_nav_menu_terms(); ?>

	<?php// do_action( 'rss2_head' ); ?>

<?php if ( $post_ids ) {
	global $wp_query;
	$wp_query->in_the_loop = true; // Fake being in the loop.
?>
     "item": [
<?php
	// 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" );

	// Begin Loop
	foreach ( $posts as $post ) {
		setup_postdata( $post );
		$is_sticky = is_sticky( $post->ID ) ? 1 : 0;
?>
    {
		"title": <?php echo json_encode(apply_filters( 'the_title_rss', $post->post_title )); ?>,
		"link": "<?php the_permalink_rss() ?>",
		"pubDate": "<?php echo mysql2date( 'D, d M Y H:i:s +0000', get_post_time( 'Y-m-d H:i:s', true ), false ); ?>",
		"dc:creator": "<?php echo get_the_author_meta( 'login' ); ?>",
		"guid": "<?php the_guid(); ?>",
		"content:encoded": <?php echo  json_encode(apply_filters( 'the_content_export', $post->post_content )); ?>,
		"excerpt:encoded": <?php echo  json_encode(apply_filters( 'the_excerpt_export', $post->post_excerpt )); ?>,
		"wp:post_id": "<?php echo $post->ID; ?>",
		"wp:post_date": "<?php echo $post->post_date; ?>",
		"wp:post_date_gmt": "<?php echo $post->post_date_gmt; ?>",
		"wp:comment_status": "<?php echo $post->comment_status; ?>",
		"wp:ping_status": "<?php echo $post->ping_status; ?>",
		"wp:post_name": "<?php echo $post->post_name; ?>",
		"wp:status": "<?php echo $post->post_status; ?>",
		"wp:post_parent": "<?php echo $post->post_parent; ?>",
		"wp:menu_order": "<?php echo $post->menu_order; ?>",
		"wp:post_type": "<?php echo $post->post_type; ?>",
		"wp:post_password": "<?php echo $post->post_password; ?>",
		"wp:is_sticky": "<?php echo $is_sticky; ?>",
<?php	if ( $post->post_type == 'attachment' ) : ?>
		"wp:attachment_url": "<?php echo wp_get_attachment_url( $post->ID ); ?>",
<?php 	endif; ?>
<?php 	wxr_post_taxonomy(); ?>
<?php	$postmeta = $wpdb->get_results( $wpdb->prepare( "SELECT * FROM $wpdb->postmeta WHERE post_id = %d", $post->ID ) );
        $flag = true;
        echo "\"wp:postmeta\": [";
		foreach ( $postmeta as $meta ) :
			if ( apply_filters( 'wxr_export_skip_postmeta', false, $meta->meta_key, $meta ) )
				continue;
            if($flag==true){
                $flag = false;
                echo "\n{\n";
            }else{
                echo ",\n{\n";
            }
		?>
                "wp:meta_key": "<?php echo $meta->meta_key; ?>",
			    "wp:meta_value": <?php echo json_encode($meta->meta_value); ?>
            }<?php	endforeach; ?>
        ],
        "wp:comment" : [
<?php	$comments = $wpdb->get_results( $wpdb->prepare( "SELECT * FROM $wpdb->comments WHERE comment_post_ID = %d AND comment_approved <> 'spam'", $post->ID ) );
		foreach ( $comments as $c ) : ?>
            {
			    "wp:comment_id": "<?php echo $c->comment_ID; ?>",
			    "wp:comment_author": "<?php echo $c->comment_author; ?>",
			    "wp:comment_author_email": "<?php echo $c->comment_author_email; ?>",
			    "wp:comment_author_url": "<?php echo esc_url_raw( $c->comment_author_url ); ?>",
			    "wp:comment_author_IP": "<?php echo $c->comment_author_IP; ?>",
			    "wp:comment_date": "<?php echo $c->comment_date; ?>",
			    "wp:comment_date_gmt": "<?php echo $c->comment_date_gmt; ?>",
			    "wp:comment_content": <?php echo  json_encode($c->comment_content); ?>,
			    "wp:comment_approved": "<?php echo $c->comment_approved; ?>",
			    "wp:comment_type": "<?php echo $c->comment_type; ?>",
			    "wp:comment_parent": "<?php echo $c->comment_parent; ?>",
			    "wp:comment_user_id": "<?php echo $c->user_id; ?>",
                "wp:commentmeta": [
<?php		$c_meta = $wpdb->get_results( $wpdb->prepare( "SELECT * FROM $wpdb->commentmeta WHERE comment_id = %d", $c->comment_ID ) );
			foreach ( $c_meta as $meta ) : ?>
			        {
				        "wp:meta_key": "<?php echo $meta->meta_key; ?>",
				        "wp:meta_value": "<?php echo  json_encode($meta->meta_value); ?>"
			        },
<?php		endforeach; ?>
		        ]
            <?php
            if ($c == end($comments))
                echo "\n}\n";
            else
                echo "\n},\n";
            ?>
<?php	endforeach; ?>
       ]
        <?php
        if ($post == end($posts))
            echo "\n}\n";
        else
            echo "\n},\n";
        ?>
<?php
	}
	}
} ?>
    ]
}
}
<?php
}

hi just wondering is the json import feature done,