groups_invite_user( array|string $args = '' )

function groups_invite_user( $args = '' ) {
	$bp = buddypress();

	$args = bp_parse_args( $args, array(
		'user_id'       => false,
		'group_id'      => false,
		'inviter_id'    => bp_loggedin_user_id(),
		'date_modified' => bp_core_current_time(),
		'is_confirmed'  => 0
	), 'groups_invite_user' );
	extract( $args, EXTR_SKIP );

	if ( ! $user_id || ! $group_id || ! $inviter_id ) {
		return false;
	}

	// If the user has already requested membership, accept the request.
	if ( $membership_id = groups_check_for_membership_request( $user_id, $group_id ) ) {
		groups_accept_membership_request( $membership_id, $user_id, $group_id );

	// Otherwise, create a new invitation.
	} elseif ( ! groups_is_user_member( $user_id, $group_id ) && ! groups_check_user_has_invite( $user_id, $group_id, 'all' ) ) {
		$invite                = new BP_Groups_Member;
		$invite->group_id      = $group_id;
		$invite->user_id       = $user_id;
		$invite->date_modified = $date_modified;
		$invite->inviter_id    = $inviter_id;
		$invite->is_confirmed  = $is_confirmed;

		if ( !$invite->save() )
			return false;

		// update user meta with invite message for a group
		if ( ! empty( $bp->groups->invites_message ) ) {
			update_user_meta( $user_id, 'bp_group_invite_message_' . $group_id, $bp->groups->invites_message );
		}

		/**
		 * Fires after the creation of a new group invite.
		 *
		 * @since BuddyPress 1.0.0
		 *
		 * @param array $args Array of parsed arguments for the group invite.
		 */
		do_action( 'groups_invite_user', $args );
	}

	return true;
}