yii2文件扩展名验证不起作用

我的模型中有这样的规则

public function rules()
{
    return [
        [['tbl_data_induk_mahasiswa_id'], 'required'],
        [['tbl_data_induk_mahasiswa_id'], 'integer'],
        [['nama'], 'file','extensions'=>'png,jpg','maxSize' => 1024000,'tooBig' => 'Size maksimum adalah 1 MB'],

        [['nama'], 'string', 'max' => 300],

        [['tbl_data_induk_mahasiswa_id'], 'unique'],
        [['tbl_data_induk_mahasiswa_id'], 'exist', 'skipOnError' => true, 'targetClass' => TblDataIndukMahasiswa::className(), 'targetAttribute' => ['tbl_data_induk_mahasiswa_id' => 'id']],
    ];
}

我有这样的形式

<?php
use yii\helpers\Html;
//use yii\widgets\ActiveForm;
echo Html::beginForm(
     ['mahasiswa-foto-biodata/update'],
     'post',
     ['enctype' => 'multipart/form-data'] //if you want to upload file with post
); ?>
<div class="form-group form-file-upload form-file-multiple">
    <?= Html::activeFileInput(
        $model,
        'nama',
        ['class' => 'inputFileHidden', 'multiple' => '']
    ); ?>
    <div class="input-group">
        <?= Html::activeTextInput(
            $model,
            'nama', 
            [
                'class' => 'form-control inputFileVisible',
                'placeholder' => 'Single File',
            ]
        ); ?>
        <span class="input-group-btn">
            <button type="button" class="btn btn-fab btn-round btn-primary">
                <i class="material-icons">attach_file</i>
            </button>
        </span>
    </div>
</div> 
<div class="form-group">
<?= Html::submitButton('Save', ['class' => 'btn btn-success']) ?>
</div>  
<?= Html::endForm(); ?>

我无法使用activeForm小部件，因为我必须创建适合我的模板的html表单，该表单有效，文件成功上传，问题是每个tipe文件都成功上传，不仅是png或jpg，而且如果我更改了最大规则nama来[['nama'], 'string', 'max' => 2],，然后我上载有名称的长度超过两个文件不能被上传的文件。

有什么帮助吗？