if (!YII_ENV_TEST) {
     $config['components']['db']['dsn'] = 'mysql:host=localhost;dbname=default';
     $config['components']['db']['username'] = 'root';
     $config['components']['db']['password'] = '';
} else {
     $config['components']['db']['dsn'] = 'mysql:host=production;dbname=default';
     $config['components']['db']['username'] = 'root';
     $config['components']['db']['password'] = '';
}

<?php
return [
    'components' => [
        'db' => [
            'class' => 'yiidbConnection',
            'dsn' => 'mysql:host=localhost;dbname=yii2advanced',
            'username' => 'root',
            'password' => '',
            'charset' => 'utf8',
        ],
        'mailer' => [
            'class' => 'yiiswiftmailerMailer',
            'viewPath' => '@common/mail',
            // send all mails to a file by default. You have to set
            // 'useFileTransport' to false and configure a transport
            // for the mailer to send real emails.
            'useFileTransport' => true,
        ],
    ],
];

<?php
return [
    'components' => [
        'db' => [
            'class' => 'yiidbConnection',
            'dsn' => 'mysql:host=localhost;dbname=y2',
            'username' => 'root',
            'password' => '',
            'charset' => 'utf8',
        ],
        'mailer' => [
            'class' => 'yiiswiftmailerMailer',
            'viewPath' => '@common/mail',
            // send all mails to a file by default. You have to set
            // 'useFileTransport' to false and configure a transport
            // for the mailer to send real emails.
            'useFileTransport' => true,
        ],
    ],
];

<?php
return [
    'components' => [
        'db' => [
            'class' => 'yiidbConnection',
            'dsn' => 'mysql:host=test.mysql.ukraine.com.ua;dbname=benzinof_yii',
            'username' => 'test_yii',
            'password' => '76dk9fkr',
            'charset' => 'utf8',
        ],
        'mailer' => [
            'class' => 'yiiswiftmailerMailer',
            'viewPath' => '@common/mail',
            // send all mails to a file by default. You have to set
            // 'useFileTransport' to false and configure a transport
            // for the mailer to send real emails.
            'useFileTransport' => true,
        ],
    ],
];