yii2.0实现验证用户名与邮箱功能

<?php
use yii\helpers\html;
use yii\bootstrap\activeform;

/* @var $this yii\web\view */
/* @var $form yii\bootstrap\activeform */
/* @var $model \frontend\models\signupform */

$this->title = '注册';
$this->params['breadcrumbs'][] = $this->title;
?>
<div class="site-signup">
 <h1><?= html::encode($this->title) ?></h1>

 <p>please fill out the following fields to signup:</p>

 <div class="row">
  <div class="col-lg-5">
   <?php $form = activeform::begin([
    'id' => 'form-signup',
    'enableajaxvalidation' => true,
    'enableclientvalidation' => true,
   ]); ?>
    
    <?= $form->field($model, 'username') ?>
    <?= $form->field($model, 'email') ?>
    <?= $form->field($model, 'password')->passwordinput() ?>
    <?= $form->field($model, 'password_compare')->passwordinput() ?>
    
    <div class="form-group">
     <?= html::submitbutton('signup', ['class' => 'btn btn-primary', 'name' => 'signup-button']) ?>
    </div>
    
   <?php activeform::end(); ?>
  </div>
 </div>
</div>

public function actionsignup()
 {
  $model = new signupform();
  
  $model->load($_post);
  if (yii::$app->request->isajax) {
   yii::$app->response->format = \yii\web\response::format_json;
   return \yii\bootstrap\activeform::validate($model);
  }
  
  if ($model->load(yii::$app->request->post())) {
   if ($user = $model->signup()) {
    if (yii::$app->getuser()->login($user)) {
     return $this->gohome();
    }
   }
  }

  return $this->render('signup', [
   'model' => $model,
  ]);
 }

use common\models\user;
use yii\base\model;
use yii;

/**
 * signup form
 */
class signupform extends model
{
 public $username;
 public $email;
 public $password;
 public $password_compare;

 /**
  * @inheritdoc
  */
 public function rules()
 {
  return [
   ['username', 'filter', 'filter' => 'trim'],
   ['username', 'required'],
   ['username', 'unique', 'targetclass' => '\common\models\user', 'message' => '用户名已存在.'],
   ['username', 'string', 'min' => 2, 'max' => 255],

   ['email', 'filter', 'filter' => 'trim'],
   ['email', 'required'],
   ['email', 'email'],
   ['email', 'unique', 'targetclass' => '\common\models\user', 'message' => '邮箱名已存在.'],

   [['password', 'password_compare'], 'required'],
   [['password', 'password_compare'], 'string', 'min' => 6, 'max' => 16, 'message' => '{attribute}是6-16位数字或字母'],
   ['password_compare', 'compare', 'compareattribute' => 'password', 'message' => '两次密码不一致'],
  ];
 }

 /**
  * signs user up.
  *
  * @return user|null the saved model or null if saving fails
  */
 public function signup()
 {
  if ($this->validate()) {
   $user = new user();
   $user->username = $this->username;
   $user->email = $this->email;
   $user->setpassword($this->password);
   $user->generateauthkey();
   if ($user->save()) {
    return $user;
   }
  }

  return null;
 }
}