SimplePie - example method to list what information we can retrieve about a feed as a whole and for single items when looping through

simplepie_example.php

<?php
defined( 'ABSPATH' ) OR exit;
/**
 * Plugin Name: (WCM) RSS Importer
 */

add_action( 'plugins_loaded', array( 'WCMRSSImporterBootstrap', 'init' ) );
class WCMRSSImporterBootstrap
{
  protected static $instance = null;

	public $page_hook = '';

	private $feed_URl = 'http://www.onthesnow.com/austria/snow-rss.html';

	public static function init()
	{
		null === self::$instance AND self::$instance = new self;
		return self::$instance;
	}

	public function __construct()
	{
		// Normally the textdomain is loaded on `init`,
		// so other plugins can replace it on `load_textdomain`.
		// We don't use it as we add & remove the file on demand to save memory
		# add_action( 'init', array( $this, 'load_l18n' ) );

		add_action( 'admin_menu', array( $this, 'add_admin_page' ) );

		add_action( 'wp_feed_options', array( $this, 'feed_options' ) );
		add_filter( 'http_request_args', array( $this, 'wp_http_api_request_args' ), 10, 2 );

		// Uncomment the following line if you want a custom feed cache lifetime
		# add_filter( 'wp_feed_cache_transient_lifetime', array( $this, 'feed_lifetime' ) );
	}

	public function load_l18n()
	{
		// No need to call it outside admin, as this is only an importer.
		if ( ! is_admin() )
			return;

		load_plugin_textdomain(
			'rss_importer',
			false,
			// Language files should reside in a subfolder named `lang`.
			plugin_basename( dirname( __FILE__ ) ).'/lang'
		);
	}

	public function unload_l18n()
	{
		unset( $GLOBALS['l10n']['rss_importer'] );
	}

	public function feed_options( &$feed )
	{
		remove_filter( current_filter(), array( $this, __FUNCTION__ ) );

		// Uncomment the following line if you're sure it's a feed
		// and SimplePie doesn't recognize it as such.
		# $feed->force_feed( true );

		# var_dump( $feed );
	}

	public function wp_http_api_request_args( $defaults, $url )
	{
		remove_filter( current_filter(), array( $this, __FUNCTION__ ) );

		# var_dump( $defaults, $url );

		return wp_parse_args( array(
			// Uncomment the following line if you got a problem
			// with a non-verified SSL certificate.
			# 'sslverify' => false
		), $defaults );
	}

	public function feed_lifetime( $seconds )
	{
		return HOUR_IN_SECONDS * 12 + ( rand( 0, 1 ) * MINUTE_IN_SECONDS );
	}

	public function add_admin_page()
	{
		$this->load_l18n();
		$this->page_hook = add_management_page(
			__( 'SimplePie RSS Example', 'rss_importer' ),
			__( 'SimplePie RSS Import', 'rss_importer' ),
			'manage_options',
			'rss-import',
			array( $this, 'admin_page_cb' )
		);
		$this->unload_l18n();
	}

	public function admin_page_cb()
	{
		$this->load_l18n();

		screen_icon();
		?>
		<h1><?php _e( 'Example RSS Output:', 'rss_importer' ); ?></h1>
		<?php
		// Include Feed stuff
		include_once( ABSPATH.WPINC.'/feed.php' );

		// Get a SimplePie feed object from the specified feed source.
		$feed = fetch_feed( $this->feed_URl );

		if ( is_wp_error( $feed ) )
			return printf(
				'%s %s',
				$feed->get_error_code(),
				$feed->get_error_message()
			);

		// Figure out how many total items there are, but limit it to 5.
		$feed_items_nr = $feed->get_item_quantity( 5 );

		$this->get_feed_data( $feed, $feed_items_nr );

		// Build an array of all the items, starting with element 0 (first element).
		$feed_items = $feed->get_items( 0, $feed_items_nr );

		if ( 0 === $feed_items_nr )
			return printf(
				'<ul><li>%s</li></ul>',
				__( 'No items', 'rss_importer' )
			);

		_e( '<h2>Items</h2>', 'rss_importer' );
		?>
		<ul>
			<?php
			foreach ( $feed_items as $item )
				$this->get_item_data( $item );
			?>
		</ul>

		<?php
		// Avoid memory leaks
		$feed->__destruct();
		unset( $feed, $feed_items, $feed_items_nr );
		$this->unload_l18n();
	}

	public function get_feed_data( $feed, $feed_items_nr )
	{

		$feed_data = array(
			'Items'        => $feed_items_nr,
			'Title'        => $feed->get_title(),
			'Description'  => $feed->get_description(),
			'Type'         => $feed->get_type(),
			'Author'       => $feed->get_author(),
			'Authors'      => $feed->get_authors(),
			'Contributor'  => $feed->get_contributor(),
			'Contributors' => $feed->get_contributors(),
			'Copyright'    => $feed->get_copyright(),
			'Encoding'     => $feed->get_encoding(),
			'Language'     => $feed->get_language(),
			'Permalink'    => $feed->get_permalink(),
			'Lat'          => $feed->get_latitude(),
			'Lng'          => $feed->get_longitude(),
			'Categories'   => $feed->get_categories(),
			'Feed Image'   => sprintf( '<p><a href="%s" title="%s"><img src="%s" title="%s" width="%s" height="%s" /></a></p>',
				$feed->get_image_link(),
				$feed->get_image_title(),
				$feed->get_image_url(),
				$feed->get_image_title(),
				$feed->get_image_width(),
				$feed->get_image_height()
			),
			'Link'         => sprintf( '<p><a href="%s" title="%s">%s</a></p>',
				$feed->get_base(),
				$feed->get_title(),
				$feed->get_title()
			)
		);

		echo '<table class="widefat">';
		foreach ( $feed_data as $desc => $item )
			echo "<tr><td class='row-title'>{$desc}</td><td>{$item}</td>";
		echo "{$out}</table>";
	}

	public function get_item_data( $item )
	{
		// Access to the parent element
		# $parent = $item->get_feed();
		# var_dump( $parent );

		$link_title = sprintf(
			__( 'Posted on %s', 'my-text-domain' ),
			$item->get_date('U')
				? date_i18n( get_option('date_format'), $item->get_date('U') )
				: __( 'unknown date and time', 'rss_importer' )
		);
		?>
		<li>
			<h2>
				<a href="<?php echo esc_url( $item->get_permalink() ); ?>"
				   title="<?php echo $link_title; ?>">
					<?php echo esc_html( $item->get_title() ); ?>
				</a>
			</h2>
			<table class="widefat">
				<?php
				foreach ( array(
					'Description'    => $item->get_description(),
					'ID'             => $item->get_id(),
					'Base'           => $item->get_base(),
					# 'Item Tags'      => $item->get_item_tags(),
					'Contributor'    => $item->get_contributor(),
					'Link'           => sprintf(
					'<a href="%s" title="%s">%s</a>',
						$item->get_link(),
						$item->get_title(),
						$item->get_title()
					),
					'Copyright'      => $item->get_copyright(),
					'Source'         => $item->get_source(),
					'Author'         => $item->get_author(),
					'Content'        => $item->get_content(),
					'Enclosure'      => $item->get_enclosure(),
					# 'Enclosures'     => var_export( $item->get_enclosures(), true ),
					'Lat'            => $item->get_latitude(),
					'Lng'            => $item->get_longitude(),
					'Date'           => $item->get_date('U')
						? date_i18n( get_option('date_format'), $item->get_date('U') )
						: '&mdash;',
					'Updated Date'   => $item->get_updated_date('U')
						? date_i18n( get_option('date_format'), $item->get_updated_date('U') )
						: '&mdash;',
					'Local Date'     => $item->get_local_date('%c'),
					'GMDate'         => $item->get_gmdate('U')
						? date_i18n( get_option('date_format'), $item->get_gmdate('U') )
						: '&mdash;',
					'Updated GMDate' => $item->get_updated_gmdate('U')
						? date_i18n( get_option('date_format'), $item->get_updated_gmdate('U') )
						: '&mdash;',
				) as $desc => $part )
					echo "<tr><td class='row-title'>{$desc}</td><td>{$part}</td></tr>";
				?>
			</table>
		</li>
		<?php
	}
}