Q:

The configuration for the "modules" component must contain a "class" element

I have define a module named `admin' in yii2.
I have registered this module in  web.php config file.
But when I try to access this I face with an error.
here is my web.php
<?php

$params = require(__DIR__ . '/params.php');

$config = [
    'id' => 'basic',
    'basePath' => dirname(__DIR__),
    'language'=>'fa_ir',
    'bootstrap' => ['log'],
    'components' => [
        'request' => [
            // !!! insert a secret key in the following (if it is empty) - this is required by cookie validation
            'cookieValidationKey' => 'SiMhYyhP2MZ_BAi321KfDHFk5uleQFa9',
        ],
        'jdate' => [
            'class' => 'jDate\DateTime'
        ],
        'cache' => [
            'class' => 'yii\caching\FileCache',
        ],
        'user' => [
            'identityClass' => 'app\models\User',
            'enableAutoLogin' => true,
        ],
        'errorHandler' => [
            'errorAction' => 'site/error',
        ],
        'modules' => [
            'admin' => [
                'class' => 'app\modules\admin\Module',
            ],
        ],
        'mailer' => [
            'class' => 'yii\swiftmailer\Mailer',
            // 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' => false,
            'transport' => [
                'class' => 'Swift_SmtpTransport',
                'host' => 'smtp.gmail.com',
                'username' => 'pishevaris@gmail.com',
                'password' => 'bhtk1368',
                'port' => '587',
                'encryption' => 'tls',
            ],
        ],
        'log' => [
            'traceLevel' => YII_DEBUG ? 3 : 0,
            'targets' => [
                [
                    'class' => 'yii\log\FileTarget',
                    'levels' => ['error', 'warning'],
                ],
            ],
        ],
        'urlManager' => [
            'class' => 'yii\web\UrlManager',
            // Disable index.php
            'showScriptName' => false,
            // Disable r= routes
            'enablePrettyUrl' => true,
            'rules' => array(
                '<controller:\w+>/<id:\d+>' => '<controller>/view',
                '<controller:\w+>/<action:\w+>/<id:\d+>' => '<controller>/<action>',
                '<controller:\w+>/<action:\w+>' => '<controller>/<action>',
            ),
        ],
        'db' => require(__DIR__ . '/db.php'),
    ],
    'params' => $params,
];

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;

here is my Module class:
<?php

namespace app\modules\admin;

class Module extends \yii\base\Module
{
    public $controllerNamespace = 'app\modules\admin\controllers';

    public function init()
    {
        parent::init();

        // custom initialization code goes here
    }
}

but when I try to access mysite/admin/default/index I face The configuration for the "modules" component must contain a "class" element error

A:

Please define module in out side of component. Like
<?php

$params = require(__DIR__ . '/params.php');

$config = [
    'id' => 'basic',
    'basePath' => dirname(__DIR__),
    'language'=>'fa_ir',
    'bootstrap' => ['log'],
    'components' => [
        'request' => [
            // !!! insert a secret key in the following (if it is empty) - this is required by cookie validation
            'cookieValidationKey' => 'SiMhYyhP2MZ_BAi321KfDHFk5uleQFa9',
        ],
        'jdate' => [
            'class' => 'jDate\DateTime'
        ],
        'cache' => [
            'class' => 'yii\caching\FileCache',
        ],
        'user' => [
            'identityClass' => 'app\models\User',
            'enableAutoLogin' => true,
        ],
        'errorHandler' => [
            'errorAction' => 'site/error',
        ],
        'mailer' => [
            'class' => 'yii\swiftmailer\Mailer',
            // 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' => false,
            'transport' => [
                'class' => 'Swift_SmtpTransport',
                'host' => 'smtp.gmail.com',
                'username' => 'pishevaris@gmail.com',
                'password' => 'bhtk1368',
                'port' => '587',
                'encryption' => 'tls',
            ],
        ],
        'log' => [
            'traceLevel' => YII_DEBUG ? 3 : 0,
            'targets' => [
                [
                    'class' => 'yii\log\FileTarget',
                    'levels' => ['error', 'warning'],
                ],
            ],
        ],
        'urlManager' => [
            'class' => 'yii\web\UrlManager',
            // Disable index.php
            'showScriptName' => false,
            // Disable r= routes
            'enablePrettyUrl' => true,
            'rules' => array(
                '<controller:\w+>/<id:\d+>' => '<controller>/view',
                '<controller:\w+>/<action:\w+>/<id:\d+>' => '<controller>/<action>',
                '<controller:\w+>/<action:\w+>' => '<controller>/<action>',
            ),
        ],
        'db' => require(__DIR__ . '/db.php'),
    ],
    'modules' => [
        'admin' => [
            'class' => 'app\modules\admin\Module',
        ],
    ],
    'params' => $params,
];

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;

