composer require kris/laravel-form-builder

Using version ^1.20 for kris/laravel-form-builder
./composer.json has been updated
Loading composer repositories with package information
Updating dependencies (including require-dev)
Package operations: 2 installs, 0 updates, 0 removals
  - Installing laravelcollective/html (v5.8.0): Downloading (100%)
  - Installing kris/laravel-form-builder (1.20.0): Downloading (100%)
Writing lock file
Generating optimized autoload files
> Illuminate\Foundation\ComposerScripts::postAutoloadDump
> @php artisan package:discover --ansi

In MemcachedConnector.php line 69:

  Class 'Memcached' not found

.envでmemocachedを有効にしているとエラーが出ので

SESSION_DRIVER=memcached
↓
SESSION_DRIVER=file