get_bookmark() WordPress Function

function get_bookmark( $bookmark, $output = OBJECT, $filter = 'raw' ) {
	global $wpdb;

	if ( empty( $bookmark ) ) {
		if ( isset( $GLOBALS['link'] ) ) {
			$_bookmark = & $GLOBALS['link'];
		} else {
			$_bookmark = null;
		}
	} elseif ( is_object( $bookmark ) ) {
		wp_cache_add( $bookmark->link_id, $bookmark, 'bookmark' );
		$_bookmark = $bookmark;
	} else {
		if ( isset( $GLOBALS['link'] ) && ( $GLOBALS['link']->link_id == $bookmark ) ) {
			$_bookmark = & $GLOBALS['link'];
		} else {
			$_bookmark = wp_cache_get( $bookmark, 'bookmark' );
			if ( ! $_bookmark ) {
				$_bookmark = $wpdb->get_row( $wpdb->prepare( "SELECT * FROM $wpdb->links WHERE link_id = %d LIMIT 1", $bookmark ) );
				if ( $_bookmark ) {
					$_bookmark->link_category = array_unique( wp_get_object_terms( $_bookmark->link_id, 'link_category', array( 'fields' => 'ids' ) ) );
					wp_cache_add( $_bookmark->link_id, $_bookmark, 'bookmark' );
				}
			}
		}
	}

	if ( ! $_bookmark ) {
		return $_bookmark;
	}

	$_bookmark = sanitize_bookmark( $_bookmark, $filter );

	if ( OBJECT === $output ) {
		return $_bookmark;
	} elseif ( ARRAY_A === $output ) {
		return get_object_vars( $_bookmark );
	} elseif ( ARRAY_N === $output ) {
		return array_values( get_object_vars( $_bookmark ) );
	} else {
		return $_bookmark;
	}
}