wp_insert_link

function wp_insert_link( $linkdata, $wp_error = false ) {
	global $wpdb;

	$defaults = array(
		'link_id'     => 0,
		'link_name'   => '',
		'link_url'    => '',
		'link_rating' => 0,
	);

	$parsed_args = wp_parse_args( $linkdata, $defaults );
	$parsed_args = wp_unslash( sanitize_bookmark( $parsed_args, 'db' ) );

	$link_id   = $parsed_args['link_id'];
	$link_name = $parsed_args['link_name'];
	$link_url  = $parsed_args['link_url'];

	$update = false;
	if ( ! empty( $link_id ) ) {
		$update = true;
	}

	if ( '' === trim( $link_name ) ) {
		if ( '' !== trim( $link_url ) ) {
			$link_name = $link_url;
		} else {
			return 0;
		}
	}

	if ( '' === trim( $link_url ) ) {
		return 0;
	}

	$link_rating      = ( ! empty( $parsed_args['link_rating'] ) ) ? $parsed_args['link_rating'] : 0;
	$link_image       = ( ! empty( $parsed_args['link_image'] ) ) ? $parsed_args['link_image'] : '';
	$link_target      = ( ! empty( $parsed_args['link_target'] ) ) ? $parsed_args['link_target'] : '';
	$link_visible     = ( ! empty( $parsed_args['link_visible'] ) ) ? $parsed_args['link_visible'] : 'Y';
	$link_owner       = ( ! empty( $parsed_args['link_owner'] ) ) ? $parsed_args['link_owner'] : get_current_user_id();
	$link_notes       = ( ! empty( $parsed_args['link_notes'] ) ) ? $parsed_args['link_notes'] : '';
	$link_description = ( ! empty( $parsed_args['link_description'] ) ) ? $parsed_args['link_description'] : '';
	$link_rss         = ( ! empty( $parsed_args['link_rss'] ) ) ? $parsed_args['link_rss'] : '';
	$link_rel         = ( ! empty( $parsed_args['link_rel'] ) ) ? $parsed_args['link_rel'] : '';
	$link_category    = ( ! empty( $parsed_args['link_category'] ) ) ? $parsed_args['link_category'] : array();

	// Make sure we set a valid category.
	if ( ! is_array( $link_category ) || 0 === count( $link_category ) ) {
		$link_category = array( get_option( 'default_link_category' ) );
	}

	if ( $update ) {
		if ( false === $wpdb->update( $wpdb->links, compact( 'link_url', 'link_name', 'link_image', 'link_target', 'link_description', 'link_visible', 'link_owner', 'link_rating', 'link_rel', 'link_notes', 'link_rss' ), compact( 'link_id' ) ) ) {
			if ( $wp_error ) {
				return new WP_Error( 'db_update_error', __( 'Could not update link in the database.' ), $wpdb->last_error );
			} else {
				return 0;
			}
		}
	} else {
		if ( false === $wpdb->insert( $wpdb->links, compact( 'link_url', 'link_name', 'link_image', 'link_target', 'link_description', 'link_visible', 'link_owner', 'link_rating', 'link_rel', 'link_notes', 'link_rss' ) ) ) {
			if ( $wp_error ) {
				return new WP_Error( 'db_insert_error', __( 'Could not insert link into the database.' ), $wpdb->last_error );
			} else {
				return 0;
			}
		}
		$link_id = (int) $wpdb->insert_id;
	}

	wp_set_link_cats( $link_id, $link_category );

	if ( $update ) {
		/**
		 * Fires after a link was updated in the database.
		 *
		 * @since 2.0.0
		 *
		 * @param int $link_id ID of the link that was updated.
		 */
		do_action( 'edit_link', $link_id );
	} else {
		/**
		 * Fires after a link was added to the database.
		 *
		 * @since 2.0.0
		 *
		 * @param int $link_id ID of the link that was added.
		 */
		do_action( 'add_link', $link_id );
	}
	clean_bookmark_cache( $link_id );

	return $link_id;
}