1. After running the init command in Yii2, an error occurred: yii\web\Request::cookieValidationKey must be configured with a secret key. See Figure 1.

2. I finally decided to improve the set of files under the environments directory, because this is a copied new application. During the “generate cookie validation key in” step, I confirmed that the file corresponding to the domain https://tougao.apply.local was missing: generate cookie validation key in papersubmission/config/main-local.php. See Figure 2.

PS C:\wwwroot\apply-server\src> ./init
Yii Application Initialization Tool v1.0
Which environment do you want the application to be initialized in?
[0] Development
[1] Production
Your choice [0-1, or "q" to quit] 0
Initialize the application under 'Development' environment? [yes|no] yes
Start initialization ...
exist api/config/main-local.php
...overwrite? [Yes|No|All|Quit] All
overwrite api/config/main-local.php
unchanged api/config/params-local.php
unchanged backend/config/codeception-local.php
overwrite backend/config/main-local.php
unchanged backend/config/params-local.php
unchanged backend/config/test-local.php
unchanged backend/web/index-test.php
unchanged backend/web/index.php
unchanged backend/web/robots.txt
overwrite common/config/codeception-local.php
overwrite common/config/main-local.php
overwrite common/config/params-local.php
unchanged common/config/test-local.php
unchanged console/config/main-local.php
unchanged console/config/params-local.php
unchanged console/config/test-local.php
unchanged frontend/config/codeception-local.php
overwrite frontend/config/main-local.php
unchanged frontend/config/params-local.php
unchanged frontend/config/test-local.php
unchanged frontend/web/index-test.php
unchanged frontend/web/index.php
unchanged frontend/web/robots.txt
overwrite management/config/main-local.php
unchanged management/config/params-local.php
unchanged papersubmission/config/main-local.php
unchanged papersubmission/config/params-local.php
unchanged yii
unchanged yii_test
unchanged yii_test.bat
generate cookie validation key in backend/config/main-local.php
generate cookie validation key in common/config/codeception-local.php
generate cookie validation key in frontend/config/main-local.php
generate cookie validation key in management/config/main-local.php
generate cookie validation key in api/config/main-local.php
chmod 0777 backend/runtime
chmod 0777 backend/web/assets
chmod 0777 console/runtime
chmod 0777 frontend/runtime
chmod 0777 frontend/web/assets
chmod 0777 api/runtime
chmod 0777 api/web/assets
chmod 0777 management/runtime
chmod 0777 management/web/assets
chmod 0755 yii
chmod 0755 yii_test
... initialization completed.
3. Copy /environments/dev/frontend to /environments/dev/papersubmission, copy /environments/prod/frontend to /environments/prod/papersubmission, and then edit /environments/index.php to add the configuration items related to papersubmission. See Figure 3.

4. After running the init command again in Yii2, the error no longer occurs.
