yii2 modifies the login module in the default demo to connect to the database

<?php

namespace app\models;

class User extends \yii\base\Object implements \yii\web\IdentityInterface
{
    public $id;
    public $username;
    public $password;
    public $authKey;
    public $accessToken;

    private static $users = [
        '100' => [
            'id' => '100',
            'username' => 'admin',
            'password' => 'admin',
            'authKey' => 'test100key',
            'accessToken' => '100-token',
        ],
    ];

    /**
     * @inheritdoc
     */
    public static function findIdentity($id)
    {
        return isset(self::$users[$id]) ? new static(self::$users[$id]) : null;
    }

    /**
     * @inheritdoc
     */
    public static function findIdentityByAccessToken($token, $type = null)
    {
        foreach (self::$users as $user) {
            if ($user['accessToken'] === $token) {
                return new static($user);
            }
        }

        return null;
    }

    /**
     * Finds user by username
     *
     * @param  string      $username
     * @return static|null
     */
    public static function findByUsername($username)
    {
        foreach (self::$users as $user) {
            if (strcasecmp($user['username'], $username) === 0) {
                return new static($user);
            }
        }

        return null;
    }

    /**
     * @inheritdoc
     */
    public function getId()
    {
        return $this->id;
    }

    /**
     * @inheritdoc
     */
    public function getAuthKey()
    {
        return $this->authKey;
    }

    /**
     * @inheritdoc
     */
    public function validateAuthKey($authKey)
    {
        return $this->authKey === $authKey;
    }

    /**
     * Validates password
     *
     * @param  string  $password password to validate
     * @return boolean if password provided is valid for current user
     */
    public function validatePassword($password)
    {
        return $this->password === $password;
    }
}

Change to the following code

<?php

namespace app\models;

use Yii;

class User extends \yii\db\ActiveRecord implements \yii\web\IdentityInterface
{
    public $id;
    public $username;
    public $password;
    public $authKey;
    public $accessToken;

    static private $AUTH_KEY = "authkey_test"; //remember me need this
    static private $ACCESS_TOKEN = "accesstoken_test"; // remember me need this

    public static function tableName()
    {
        return 'tb_admin';
    }

    /**
     * @return \yii\db\Connection the database connection used by this AR class.
     */
    public static function getDb()
    {
        return Yii::$app->get('db_admin');
    }

    /**
     * Finds user by username
     *
     * @param  string      $username
     * @return static|null
     */
    public static function findByUsername($username)
    {
	$user = User::find()->where(['username'=>$username])->asArray()->one();
	if(isset($user)){
            $user['authKey'] = self::$AUTH_KEY;
            $user['accessToken'] = self::$ACCESS_TOKEN;
	}
	return isset($user) ? new static($user) : null;
    }

    /**
     * Validates password
     *
     * @param  string  $password password to validate
     * @return boolean if password provided is valid for current user
     */
    public function validatePassword($password)
    {
        return $this->password === $password;
    }

    /**
     * @inheritdoc
     */
    public function getId()
    {
        return $this->id;
    }

    /**
     * @inheritdoc
     */
    public function getAuthKey()
    {
        return $this->authKey;
    }

    /**
     * @inheritdoc
     */
    public static function findIdentity($id)
    {
	$user = User::find()->where(['id'=>$id])->asArray()->one();
	if(isset($user)){
            $user['authKey'] = self::$AUTH_KEY;
            $user['accessToken'] = self::$ACCESS_TOKEN;
	}
	return isset($user) ? new static($user) : null;
    }

    /**
     * @inheritdoc
     */
    public static function findIdentityByAccessToken($token, $type = null)
    {
	return null;
    }

    /**
     * @inheritdoc
     */
    public function validateAuthKey($authKey)
    {
        return $this->authKey === $authKey;
    }
}

The above introduces how to modify the login module in the default demo of yii2 to connect to the database, including the content. I hope it will be helpful to friends who are interested in PHP tutorials.