如何解决在数据库中插入数据时的问题，Yii2？

// 配置数据库连接
$config = [
    'components' => [
        'db' => [
            'class' => 'yii\db\Connection',
            'dsn' => 'mysql:host=localhost;dbname=mydatabase',
            'username' => 'root',
            'password' => 'password',
        ],
    ],
];

// 创建模型类
class User extends \yii\db\ActiveRecord
{
    public static function tableName()
    {
        return 'user';
    }
}

// 插入数据
$user = new User();
$user->username = 'john';
$user->email = 'john@example.com';
if ($user->save()) {
    echo 'Data inserted successfully.';
} else {
    echo 'Failed to insert data.';
}