I want to run horde/components on new PHP

If you want to run horde-components on a version of PHP which is not yet reflected in packagist.org released versions:

me@mine:~/horde/components$ composer config minimum-stability dev
me@mine:~/horde/components$ composer install –ignore-platform-reqs

No composer.lock file present. Updating dependencies to latest instead of installing from lock file. See https://getcomposer.org/install for more information.
Loading composer repositories with package information
Updating dependencies
Lock file operations: 90 installs, 0 updates, 0 removals

• Locking fig/event-dispatcher-util (1.3.1)
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  Package operations: 90 installs, 0 updates, 0 removals
• Downloading horde/horde-installer-plugin (v2.5.5)
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• Installing horde/horde-installer-plugin (v2.5.5): Extracting archive
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• Installing horde/autoloader (dev-FRAMEWORK_6_0 dfb56fa): Extracting archive
• Installing horde/compress_fast (v2.0.0alpha4): Extracting archive
• Installing horde/cache (dev-FRAMEWORK_6_0 29bb731): Extracting archive
• Installing horde/stream_wrapper (v3.0.0alpha4): Extracting archive
• Installing horde/support (v3.0.0.1alpha4): Extracting archive
• Installing horde/cli (v3.0.0alpha5): Extracting archive
• Installing horde/argv (dev-FRAMEWORK_6_0 a1362b5): Extracting archive
• Installing horde/cli_modular (v3.0.0alpha4): Extracting archive
• Installing psr/log (dev-master f16e1d5): Extracting archive
• Installing php-extended/polyfill-php80-stringable (1.2.12): Extracting archive
• Installing horde/constraint (v3.0.0alpha4): Extracting archive
• Installing horde/log (v3.0.0alpha8): Extracting archive
• Installing psr/container (dev-master 7079847): Extracting archive
• Installing horde/injector (dev-FRAMEWORK_6_0 6fbc75e): Extracting archive
• Installing horde/controller (dev-FRAMEWORK_6_0 35005ea): Extracting archive
• Installing horde/crypt_blowfish (v2.0.0alpha3): Extracting archive
• Installing horde/url (v3.0.0alpha5): Extracting archive
• Installing horde/css_parser (v2.0.0alpha4): Extracting archive
• Installing horde/cssminify (v2.0.0alpha4): Extracting archive
• Installing horde/text_flowed (v3.0.0alpha4): Extracting archive
• Installing horde/secret (v3.0.0alpha4): Extracting archive
• Installing horde/idna (v2.0.0alpha4): Extracting archive
• Installing horde/text_filter (v3.0.0alpha3): Extracting archive
• Installing horde/stream_filter (v3.0.0alpha4): Extracting archive
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• Installing horde/mime (v3.0.0alpha5): Extracting archive
• Installing horde/mail (v3.0.0alpha4): Extracting archive
• Installing horde/listheaders (v2.0.0alpha4): Extracting archive
• Installing horde/icalendar (v3.0.0alpha4): Extracting archive
• Installing horde/browser (v3.0.0alpha4): Extracting archive
• Installing horde/data (v3.0.0alpha4): Extracting archive
• Installing psr/event-dispatcher (dev-master bbd9eac): Extracting archive
• Installing fig/event-dispatcher-util (1.3.1): Extracting archive
• Installing horde/eventdispatcher (dev-FRAMEWORK_6_0 8253aa9): Extracting archive
• Installing psr/http-message (dev-master 402d35b): Extracting archive
• Installing psr/http-factory (1.1.0): Extracting archive
• Installing psr/http-client (dev-master bb5906e): Extracting archive
• Installing horde/http (dev-FRAMEWORK_6_0 a98cb86): Extracting archive
• Installing horde/githubapiclient (dev-FRAMEWORK_6_0 fe17552): Extracting archive
• Installing horde/hashtable (v2.0.0alpha4): Extracting archive
• Installing horde/db (v3.0.0alpha4): Extracting archive
• Installing horde/history (v3.0.0alpha4): Extracting archive
• Installing psr/http-server-handler (dev-master 13403d4): Extracting archive
• Installing psr/http-server-middleware (dev-master 459eeb7): Extracting archive
• Installing horde/http_server (dev-FRAMEWORK_6_0 4a91669): Extracting archive
• Installing horde/javascriptminify (v2.0.0alpha4): Extracting archive
• Installing horde/lock (v3.0.0alpha4): Extracting archive
• Installing horde/logintasks (v3.0.0alpha4): Extracting archive
• Installing horde/compress (v3.0.0alpha4): Extracting archive
• Installing horde/mime_viewer (v3.0.0alpha4): Extracting archive
• Installing horde/notification (v3.0.0alpha4): Extracting archive
• Installing horde/pack (v2.0.0alpha4): Extracting archive
• Installing horde/yaml (dev-FRAMEWORK_6_0 c222d58): Extracting archive
• Installing horde/xml_element (v3.0.0alpha4): Extracting archive
• Installing horde/pear (dev-FRAMEWORK_6_0 6e99004): Extracting archive
• Installing horde/prefs (v3.0.0alpha6): Extracting archive
• Installing horde/serialize (v3.0.0alpha4): Extracting archive
• Installing horde/group (v3.0.0alpha4): Extracting archive
• Installing horde/perms (v3.0.0alpha4): Extracting archive
• Installing sabre/uri (v2.x-dev 2c21ebd): Extracting archive
• Installing sabre/xml (2.2.x-dev 01a7927): Extracting archive
• Installing sabre/vobject (4.5.x-dev ff22611): Extracting archive
• Installing sabre/event (5.1.x-dev 1538b1b): Extracting archive
• Installing sabre/http (5.1.x-dev 4c2a2c0): Extracting archive
• Installing sabre/dav (4.7.x-dev 7183a67): Extracting archive
• Installing pear/pear (dev-master 9d3ac5e): Extracting archive
• Installing pear/xml_util (dev-master a1ce442): Extracting archive
• Installing pear/structures_graph (dev-trunk 66368ac): Extracting archive
• Installing pear/console_getopt (dev-master f0098a8): Extracting archive
• Installing pear/archive_tar (1.5.0): Extracting archive
• Installing horde/view (v3.0.0alpha4): Extracting archive
• Installing horde/token (v3.0.0alpha4): Extracting archive
• Installing horde/template (v3.0.0alpha4): Extracting archive
• Installing horde/share (v3.0.0alpha4): Extracting archive
• Installing horde/sessionhandler (v3.0.0alpha3): Extracting archive
• Installing horde/core (v3.0.0alpha14): Extracting archive
• Installing horde/dav (v2.0.0alpha4): Extracting archive
• Installing horde/rpc (v3.0.0alpha5): Extracting archive
• Installing horde/release (v4.0.0alpha4): Extracting archive
• Installing horde/role (dev-FRAMEWORK_6_0 cac03aa): Extracting archive
• Installing horde/test (dev-FRAMEWORK_6_0 c512302): Extracting archive
• Installing horde/text_diff (dev-FRAMEWORK_6_0 f7cfbc2): Extracting archive
  73 package suggestions were added by new dependencies, use composer suggest to see details.
  Package php-extended/polyfill-php80-stringable is abandoned, you should avoid using it. Use php >= 8.0 instead.
  Generating autoload files
  Applying /presets for absent files in /var/config
  Looking for registry snippets from apps
  Writing app configs to /var/config dir
  Linking app configs to /web Dir
  Linking javascript tree to /web/js
  Linking themes tree to /web/themes

Beware, these constraints are there for a reason. Expect things to break in unexpected ways if versions are actually incompatible.