Exception 'ReflectionException' with message 'Class require does not exist'

 记录一下今天遇到的错误

在使用

<?= $form->field($model, 'content')->textarea() ?>

的时候报错

Exception 'ReflectionException' with message 'Class require does not exist' 

in D:phpStudyWWWvvvvendoryiisoftyii2diContainer.php:415

Stack trace:
#0 D:phpStudyWWWclecssv2vendoryiisoftyii2diContainer.php(415): ReflectionClass->__construct('require')
#1 D:phpStudyWWWclecssv2vendoryiisoftyii2diContainer.php(358): yiidiContainer->getDependencies('require')
#2 D:phpStudyWWWclecssv2vendoryiisoftyii2diContainer.php(151): yiidiContainer->build('require', Array, Array)
#3 D:phpStudyWWWclecssv2vendoryiisoftyii2BaseYii.php(344): yiidiContainer->get('require', Array, Array)
#4 D:phpStudyWWWclecssv2vendoryiisoftyii2validatorsValidator.php(206): yiiBaseYii::createObject(Array)

错误原因是：

public function rules()
{
　　return [
　　[['content'],'require'],
　　];
}
少了一个d, required