Your requirements could not be resolved to an installable set of packages.
Problem 1
- Root composer.json requires kyrne/websocket ^3.3 -> satisfiable by kyrne/websocket[3.3.0].
- kyrne/websocket 3.3.0 requires pusher/pusher-php-server ^7.0 -> found pusher/pusher-php-server[7.0.0, 7.0.1, 7.0.2] but the package is fixed to 2.6.4 (lock file version) by a partial update and that version does not match. Make sure you list it as an argument for the update command.
Use the option --with-all-dependencies (-W) to allow upgrades, downgrades and removals for packages currently locked to specific versions.
Installation failed, reverting ./composer.json and ./composer.lock to their original content.