wighair/environments/dev/apphtml5/config/main-local.php

<?php

$config = [
    'components' => [
        'request' => [
            // !!! insert a secret key in the following (if it is empty) - this is required by cookie validation
            'cookieValidationKey' => 'FoOwzm-NS4xrnCPaCEhUP0QYOmnAdHjL',
        ],
    ],
];

if (YII_ENV_DEV) {
    // configuration adjustments for 'dev' environment
    $config['bootstrap'][] = 'debug';
    $config['modules']['debug'] = 'yii\debug\Module';

    $config['bootstrap'][] = 'gii';
    $config['modules']['gii'] = 'yii\gii\Module';
}

return $config;