'Error when communicating with Server' on Email with attached appointment.

[mborgelt]

Hi.
When I try to open an email with attached appointment as ICS file I get 'Error when communicating with server'.
Apache error Log says:

[Fri May 29 11:41:02.664759 2026] [proxy_fcgi:error] [pid 531348:tid 531360] [remote xx.xx.xx.xx:47550] AH01071: Got error 'PHP message: PHP Fatal error:  Could not check compatibility between IMP_Ajax_Imple_ItipRequest::_handle(Variables|Horde_Variables $vars) and Horde_Core_Ajax_Imple::_handle(Horde_Variables|Horde\\Util\\Variables $vars), because class Variables is not available in /srv/horde/vendor/horde/imp/lib/Ajax/Imple/ItipRequest.php on line 64', referer: https://horde.xxxxx.xx/imp/dynamic.php?page=mailbox

Horde versions:

fig/event-dispatcher-util    1.3.1       Useful utility classes and traits for implementing the PSR events standard
horde/activesync             3.0.0beta2  ActiveSync server library
horde/alarm                  3.0.0beta1  Alarm library
horde/argv                   3.0.0beta1  Command-line argument parsing library
horde/auth                   3.0.0beta3  Authentication and user management library
horde/autoloader             3.0.0beta1  Autoloader library
horde/browser                3.0.0RC1    Browser detection library
horde/cache                  3.0.0RC2    Caching library
horde/cli                    3.0.0beta5  Command line interface library
horde/cli_modular            3.0.0beta1  Modular command line interface library
horde/composer               1.0.0beta1  Handle composer.json files and composer directory structures without composer dep...
horde/compress               3.0.0beta2  Compression library
horde/compress_fast          2.0.0beta1  Fast compression library
horde/constraint             3.0.0beta1  Modern constraint library with PHP 8.1+ type safety
horde/content                3.0.0RC1    Tagging application
horde/controller             3.0.0beta1  Controller library
horde/core                   3.0.0RC6    Core Horde Framework library
horde/crypt                  3.0.0beta5  Cryptography library
horde/crypt_blowfish         2.0.0beta2  Blowfish encryption library
horde/css_parser             2.0.0beta7  CSS parser library
horde/cssminify              2.0.0beta6  CSS minification library
horde/data                   3.0.0beta1  Data import and export library
horde/date                   3.0.0RC3    Date library
horde/date_parser            3.0.0beta1  Date parser library
horde/dav                    2.0.0beta2  WebDAV, CalDAV, and CardDAV library
horde/db                     3.0.0RC1    Database abstraction library
horde/editor                 3.0.0beta2  WYSIWYG editor library
horde/eventdispatcher        1.0.0beta3  A simple PSR-14 EventDispatcher / ListenerProvider system for Horde
horde/exception              3.0.0beta6  Exception handler library
horde/form                   3.0.0RC4    Form library
horde/group                  3.0.0beta2  User groups library supporting many backend types.
horde/hashtable              2.0.0RC3    Hash table client library
horde/history                3.0.0RC1    History tracking library
horde/horde                  6.0.0RC5    Horde base application
horde/horde-installer-plugin 3.6.0       Horde Installer Plugin for Composer
horde/hordectl               1.0.0RC1    Scenario deployer library
horde/hordeymlfile           1.0.0RC1    Handle .horde.yml file and changelog.yml file
horde/http                   3.0.0RC2    HTTP client library
horde/http_server            1.0.0RC1    HTTP Request Handling Library adhering to PSR-15 standard. This evolved out of ho...
horde/icalendar              3.0.0RC1    iCalendar and vCard library
horde/identity               1.0.0RC1    Short headline for Identity
horde/idna                   2.0.0beta2  IDNA normalization library
horde/image                  3.0.0RC3    Image library
horde/imap_client            3.0.0RC1    IMAP client library
horde/imp                    7.0.0RC3    Webmail application
horde/ingo                   4.0.0RC3    Email filter rules manager application
horde/injector               3.0.0beta4  Dependency injection container library
horde/itip                   3.0.0RC1    iTip invitation response library
horde/javascriptminify       2.0.0beta1  JavaScript minification library
horde/jwt                    1.0.0beta2  Horde RFC 7519 JSON Web Token (JWT) Library
horde/kronolith              5.0.0RC4    Calendar and scheduling application
horde/listheaders            2.0.0beta1  List headers parsing library
horde/lock                   3.0.0beta1  Resource locking library
horde/log                    3.0.0beta7  Logging library
horde/logintasks             3.0.0beta1  Login tasks library
horde/mail                   3.0.0RC2    Mail library
horde/mail_autoconfig        2.0.0beta1  Mail server autoconfiguration library
horde/managesieve            2.0.0RC2    ManageSieve client library
horde/mapi                   2.0.0alpha5 MAPI utility library
horde/mime                   3.0.0RC1    MIME library
horde/mime_viewer            3.0.0beta1  MIME viewer library
horde/mnemo                  5.0.0beta5  Notes application
horde/nag                    5.0.0RC3    Task list application
horde/nls                    3.0.0RC1    Native language support library
horde/notification           3.0.0beta1  Notification library implementing subject-observer pattern
horde/oauth                  4.0.0RC1    OAuth 1.0a, OAuth 2.0 and OpenID Connect library
horde/pack                   2.0.0beta1  Data packing library
horde/perms                  3.0.0RC1    Permissions library
horde/phpconfigfile          0.0.1RC1    Read and write config files as PHP Code
horde/prefs                  3.0.0RC3    User preferences library
horde/rdo                    3.0.0beta2  ORM (object relational-mapping) library
horde/routes                 3.0.0RC2    URL routing/mapping library
horde/rpc                    3.0.0beta4  RPC library
horde/secret                 3.0.0beta1  Secret key encryption library with authenticated encryption
horde/serialize              3.0.0beta2  Data serialization library
horde/service_weather        3.0.0alpha5 Weather service library
horde/sessionhandler         3.0.0beta2  Session handler library
horde/share                  3.0.0beta1  Resource sharing library
horde/smtp                   2.0.0beta1  SMTP and LMTP client library
horde/socket_client          3.0.0beta1  Network socket client library
horde/spellchecker           3.0.0beta1  Spellchecking library
horde/stream                 2.0.0RC1    PHP streams library
horde/stream_filter          3.0.0beta2  PHP stream filters library
horde/stream_wrapper         3.0.0beta1  PHP stream wrappers library
horde/support                3.0.0beta1  Supporting library
horde/template               3.0.0RC1    Template library (deprecated)
horde/test                   3.0.0alpha8 Unit testing library
horde/text_diff              3.0.0beta1  Text diff generation and rendering library
horde/text_filter            3.0.0RC1    Text filtering and conversion library
horde/text_flowed            3.0.0beta1  Flowed text library
horde/timeobjects            3.0.0beta1  Time-based objects application
horde/timezone               2.0.0RC1    Timezone library
horde/token                  3.0.0beta1  Tokens library
horde/translation            3.0.0beta2  Translation library
horde/tree                   3.0.0beta2  Tree rendering library
horde/turba                  5.0.0RC4    Address book application
horde/url                    3.0.0beta2  URL library
horde/util                   3.0.0beta5  Utility library
horde/version                1.0.0RC1    Handle Semantic Version 2.0.0 format and similar semantic version formats
horde/vfs                    3.0.0RC1    Virtual file system library
horde/view                   3.0.0beta1  View pattern library
horde/xml_element            3.0.0beta2  XML element library
horde/yaml                   3.0.0beta1  YAML parsing and writing library
mikepultz/netdns2            2.0.8       PHP DNS Resolver and Updater Library
pear/console_color2          0.1.2       This Class allows you to easily use ANSI console colors in your application.
pear/console_table           1.3.1       Library that makes it easy to build console style tables.
php81_bc/strftime            0.7.6       Locale-formatted strftime using IntlDateFormatter (PHP 8.1 compatible)
psr/container                2.0.2       Common Container Interface (PHP FIG PSR-11)
psr/event-dispatcher         1.0.0       Standard interfaces for event handling.
psr/http-client              1.0.3       Common interface for HTTP clients
psr/http-factory             1.1.0       PSR-17: Common interfaces for PSR-7 HTTP message factories
psr/http-message             2.0         Common interface for HTTP messages
psr/http-server-handler      1.0.2       Common interface for HTTP server-side request handler
psr/http-server-middleware   1.0.2       Common interface for HTTP server-side middleware
psr/log                      3.0.2       Common interface for logging libraries
psr/simple-cache             3.0.0       Common interfaces for simple caching
sabberworm/php-css-parser    9.3.0       Parser for CSS Files written in PHP
sabre/dav                    4.7.0       WebDAV Framework for PHP
sabre/event                  5.1.8       sabre/event is a library for lightweight event-based programming
sabre/http                   5.1.13      The sabre/http library provides utilities for dealing with http requests and resp...
sabre/uri                    2.3.4       Functions for making sense out of URIs.
sabre/vobject                4.5.8       The VObject library for PHP allows you to easily parse and manipulate iCalendar a...
sabre/xml                    2.2.11      sabre/xml is an XML library that you may not hate.
thecodingmachine/safe        3.4.0       PHP core functions that throw exceptions instead of returning FALSE on error
tinymce/tinymce              8.5.1       Web based JavaScript HTML WYSIWYG editor control.

Regards
Michael.