function bp_register_member_type( $member_type, $args = array() ) {
	$bp = buddypress();

	if ( isset( $bp->members->types[ $member_type ] ) ) {
		return new WP_Error( 'bp_member_type_exists', __( 'Member type already exists.', 'buddypress' ), $member_type );
	}

	$r = bp_parse_args( $args, array(
		'labels'        => array(),
		'has_directory' => true,
	), 'register_member_type' );

	$member_type = sanitize_key( $member_type );

	/**
	 * Filters the list of illegal member type names.
	 *
	 * - 'any' is a special pseudo-type, representing items unassociated with any member type.
	 * - 'null' is a special pseudo-type, representing users without any type.
	 * - '_none' is used internally to denote an item that should not apply to any member types.
	 *
	 * @since 2.4.0
	 *
	 * @param array $illegal_names Array of illegal names.
	 */
	$illegal_names = apply_filters( 'bp_member_type_illegal_names', array( 'any', 'null', '_none' ) );
	if ( in_array( $member_type, $illegal_names, true ) ) {
		return new WP_Error( 'bp_member_type_illegal_name', __( 'You may not register a member type with this name.', 'buddypress' ), $member_type );
	}

	// Store the post type name as data in the object (not just as the array key).
	$r['name'] = $member_type;

	// Make sure the relevant labels have been filled in.
	$default_name = isset( $r['labels']['name'] ) ? $r['labels']['name'] : ucfirst( $r['name'] );
	$r['labels'] = array_merge( array(
		'name'          => $default_name,
		'singular_name' => $default_name,
	), $r['labels'] );

	// Directory slug.
	if ( $r['has_directory'] ) {
		// A string value is intepreted as the directory slug. Otherwise fall back on member type.
		if ( is_string( $r['has_directory'] ) ) {
			$directory_slug = $r['has_directory'];
		} else {
			$directory_slug = $member_type;
		}

		// Sanitize for use in URLs.
		$r['directory_slug'] = sanitize_title( $directory_slug );
		$r['has_directory']  = true;
	} else {
		$r['directory_slug'] = '';
		$r['has_directory']  = false;
	}

	$bp->members->types[ $member_type ] = $type = (object) $r;

	/**
	 * Fires after a member type is registered.
	 *
	 * @since 2.2.0
	 *
	 * @param string $member_type Member type identifier.
	 * @param object $type        Member type object.
	 */
	do_action( 'bp_registered_member_type', $member_type, $type );

	return $type;
}