                        课程
                    
                        /后端开发
                        
                            /PHP
                        
                        /PHP之Yii2框架搭建完整博客系统

PHP Fatal Error – yii\base\ErrorException

<?php

use yii\bootstrap\ActiveForm;
$this->title = Yii::t('common', 'Create');
$this->params['breadcrumbs'][] = ['label' => Yii::t('common', 'Articles'), 'url' => ['post/index']];
$this->params['breadcrumbs'][] = $this->title;
?>
<div class="row">
	<div class="col-lg-9">
		<div class="panel-title box-title">
			<span>创建文章</span>
		</div>
		<div class="panel-body">
			<?php $form = ActiveForm::begin() ?>

			<?= $form->field($model, 'title')->textinput(['maxlength' => true]) ?>

			<?= $form->field($model, 'cat_id')->dropDownList(['1' => '分类1', '2' => '分类2']) ?>

			<?= $form->field($model, 'label_img')->textinput(['maxlength' => true]) ?>
			
			<?= $form->field($model, 'content')->textinput(['maxlength' => true]) ?>

			<?= $form->field($model, 'tags')->textinput(['maxlength' => true]) ?>
			
			<div class="form-group">
				<?= Html::submitButton("发布", ['class' => 'btn btn-seccess']) ?>
			</div>

			<?php $form = ActiveForm::end() ?>
		</div>
	</div>
	<div class="col-lg-3">
		<div class="panel-title box-title">
			<span>注意事项</span>
		</div>
		<div class="panel-body">
			<p>1.asdadadad</p>
			<p>2.asfafds</p>
		</div>
	</div>
</div>

Method yii\bootstrap\ActiveField::__toString() must not throw an exception, caught Error: Class 'frontend\models\Yii' not found

试了好久,始终调不出来创建文章的页面,命名空间的错误吗?应该怎么写