osure = explode("\n", $enc);

				// only get the first element, e.g. audio/mpeg from 'audio/mpeg mpga mp2 mp3'
				$t = preg_split('/[ \t]/', trim($enclosure[2]) );
				$type = $t[0];

				/**
				 * Filters the RSS enclosure HTML link tag for the current post.
				 *
				 * @since 2.2.0
				 *
				 * @param string $html_link_tag The HTML link tag with a URI and other attributes.
				 */
				echo apply_filters( 'rss_enclosure', '<enclosure url="' . esc_url( trim( $enclosure[0] ) ) . '" length="' . absint( trim( $enclosure[1] ) ) . '" type="' . esc_attr( $type ) . '" />' . "\n" );
			}
		}
	}
}

/**
 * Display the atom enclosure for the current post.
 *
 * Uses the global $post to check whether the post requires a password and if
 * the user has the password for the post. If not then it will return before
 * displaying.
 *
 * Also uses the function get_post_custom() to get the post's 'enclosure'
 * metadata field and parses the value to display the enclosure(s). The
 * enclosure(s) consist of link HTML tag(s) with a URI and other attributes.
 *
 * @since 2.2.0
 */
function atom_enclosure() {
	if ( post_password_required() )
		return;

	foreach ( (array) get_post_custom() as $key => $val ) {
		if ($key == 'enclosure') {
			foreach ( (array) $val as $enc ) {
				$enclosure = explode("\n", $enc);
				/**
				 * Filters the atom enclosure HTML link tag for the current post.
				 *
				 * @since 2.2.0
				 *
				 * @param string $html_link_tag The HTML link tag with a URI and other attributes.
				 */
				echo apply_filters( 'atom_enclosure', '<link href="' . esc_url( trim( $enclosure[0] ) ) . '" rel="enclosure" length="' . absint( trim( $enclosure[1] ) ) . '" type="' . esc_attr( trim( $enclosure[2] ) ) . '" />' . "\n" );
			}
		}
	}
}

/**
 * Determine the type of a string of data with the data formatted.
 *
 * Tell whether the type is text, html, or xhtml, per RFC 4287 section 3.1.
 *
 * In the case of WordPress, text is defined as containing no markup,
 * xhtml is defined as "well formed", and html as tag soup (i.e., the rest).
 *
 * Container div tags are added to xhtml values, per section 3.1.1.3.
 *
 * @link http://www.atomenabled.org/developers/syndication/atom-format-spec.php#rfc.section.3.1
 *
 * @since 2.5.0
 *
 * @param string $data Input string
 * @return array array(type, value)
 */
function prep_atom_text_construct($data) {
	if (strpos($data, '<') === false && strpos($data, '&') === false) {
		return array('text', $data);
	}

	if ( ! function_exists( 'xml_parser_create' ) ) {
		trigger_error( __( "PHP's XML extension is not available. Please contact your hosting provider to enable PHP's XML extension." ) );

		return array( 'html', "<![CDATA[$data]]>" );
	}

	$parser = xml_parser_create();
	xml_parse($parser, '<div>' . $data . '</div>', true);
	$code = xml_get_error_code($parser);
	xml_parser_free($parser);

	if (!$code) {
		if (strpos($data, '<') === false) {
			return array('text', $data);
		} else {
			$data = "<div xmlns='http://www.w3.org/1999/xhtml'>$data</div>";
			return array('xhtml', $data);
		}
	}

	if (strpos($data, ']]>') === false) {
		return array('html', "<![CDATA[$data]]>");
	} else {
		return array('html', htmlspecialchars($data));
	}
}

/**
 * Displays Site Icon in atom feeds.
 *
 * @since 4.3.0
 *
 * @see get_site_icon_url()
 */
function atom_site_icon() {
	$url = get_site_icon_url( 32 );
	if ( $url ) {
		echo "<icon>$url</icon>\n";
	}
}

/**
 * Displays Site Icon in RSS2.
 *
 * @since 4.3.0
 */
function rss2_site_icon() {
	$rss_title = get_wp_title_rss();
	if ( empty( $rss_title ) ) {
		$rss_title = get_bloginfo_rss( 'name' );
	}

	$url = get_site_icon_url( 32 );
	if ( $url ) {
		echo '
<image>
	<url>' . convert_chars( $url ) . '</url>
	<title>' . $rss_title . '</title>
	<link>' . get_bloginfo_rss( 'url' ) . '</link>
	<width>32</width>
	<height>32</height>
</image> ' . "\n";
	}
}

/**
 * Display the link for the currently displayed feed in a XSS safe way.
 *
 * Generate a correct link for the atom:self element.
 *
 * @since 2.5.0
 */
function self_link() {
	$host = @parse_url(home_url());
	/**
	 * Filters the current feed URL.
	 *
	 * @since 3.6.0
	 *
	 * @see set_url_scheme()
	 * @see wp_unslash()
	 *
	 * @param string $feed_link The link for the feed with set URL scheme.
	 */
	echo esc_url( apply_filters( 'self_link', set_url_scheme( 'http://' . $host['host'] . wp_unslash( $_SERVER['REQUEST_URI'] ) ) ) );
}

/**
 * Return the content type for specified feed type.
 *
 * @since 2.8.0
 *
 * @param string $type Type of feed. Possible values include 'rss', rss2', 'atom', and 'rdf'.
 */
function feed_content_type( $type = '' ) {
	if ( empty($type) )
		$type = get_default_feed();

	$types = array(
		'rss'      => 'application/rss+xml',
		'rss2'     => 'application/rss+xml',
		'rss-http' => 'text/xml',
		'atom'     => 'application/atom+xml',
		'rdf'      => 'application/rdf+xml'
	);

	$content_type = ( !empty($types[$type]) ) ? $types[$type] : 'application/octet-stream';

	/**
	 * Filters the content type for a specific feed type.
	 *
	 * @since 2.8.0
	 *
	 * @param string $content_type Content type indicating the type of data that a feed contains.
	 * @param string $type         Type of feed. Possible values include 'rss', rss2', 'atom', and 'rdf'.
	 */
	return apply_filters( 'feed_content_type', $content_type, $type );
}

/**
 * Build SimplePie object based on RSS or Atom feed from URL.
 *
 * @since 2.8.0
 *
 * @param mixed $url URL of feed to retrieve. If an array of URLs, the feeds are merged
 * using SimplePie's multifeed feature.
 * See also {@link ​http://simplepie.org/wiki/faq/typical_multifeed_gotchas}
 *
 * @return WP_Error|SimplePie WP_Error object on failure or SimplePie object on success
 */
function fetch_feed( $url ) {
	if ( ! class_exists( 'SimplePie', false ) ) {
		require_once( ABSPATH . WPINC . '/class-simplepie.php' );
	}

	require_once( ABSPATH . WPINC . '/class-wp-feed-cache.php' );
	require_once( ABSPATH . WPINC . '/class-wp-feed-cache-transient.php' );
	require_once( ABSPATH . WPINC . '/class-wp-simplepie-file.php' );
	require_once( ABSPATH . WPINC . '/class-wp-simplepie-sanitize-kses.php' );

	$feed = new SimplePie();

	$feed->set_sanitize_class( 'WP_SimplePie_Sanitize_KSES' );
	// We must manually overwrite $feed->sanitize because SimplePie's
	// constructor sets it before we have a chance to set the sanitization class
	$feed->sanitize = new WP_SimplePie_Sanitize_KSES();

	$feed->set_cache_class( 'WP_Feed_Cache' );
	$feed->set_file_class( 'WP_SimplePie_File' );

	$feed->set_feed_url( $url );
	/** This filter is documented in wp-includes/class-wp-feed-cache-transient.php */
	$feed->set_cache_duration( apply_filters( 'wp_feed_cache_transient_lifetime', 12 * HOUR_IN_SECONDS, $url ) );
	/**
	 * Fires just before processing the SimplePie feed object.
	 *
	 * @since 3.0.0
	 *
	 * @param object $feed SimplePie feed object (passed by reference).
	 * @param mixed  $url  URL of feed to retrieve. If an array of URLs, the feeds are merged.
	 */
	do_action_ref_array( 'wp_feed_options', array( &$feed, $url ) );
	$feed->init();
	$feed->set_output_encoding( get_option( 'blog_charset' ) );

	if ( $feed->error() )
		return new WP_Error( 'simplepie-error', $feed->error() );

	return $feed;
}