[ 'request' => [ // !!! insert a secret key in the following (if it is empty) - this is required by cookie validation 'cookieValidationKey' => '2o3ZqTWRpgn4a9Knyb6iGva0SDKD31Lq', ], ], ]; if (YII_ENV_DEV) { // configuration adjustments for 'dev' environment $config['bootstrap'][] = 'debug'; $config['modules']['debug'] = [ 'class' => 'yii\debug\Module', ]; $config['bootstrap'][] = 'gii'; $config['modules']['gii'] = [ 'class' => 'yii\gii\Module', ]; } return $config;