CREATE TABLE `easy_upload` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(100) DEFAULT NULL,
  `surname` varchar(100) DEFAULT NULL,
  `photo` varchar(255) DEFAULT NULL,
  `photos` text,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8

<?php

namespace backend\models;

use Yii;
use \yii\web\UploadedFile;

class EasyUpload extends \yii\db\ActiveRecord
{
    public $upload_foler ='uploads';

// ....

public function rules()
{
    return [
        [['name', 'surname'], 'required'],
        [['name', 'surname'], 'string', 'max' => 100],
        [['photo'], 'file',
          'skipOnEmpty' => true,
          'extensions' => 'png,jpg'
        ]
    ];
}

public function upload($model,$attribute)
{
    $photo  = UploadedFile::getInstance($model, $attribute);
      $path = $this->getUploadPath();
    if ($this->validate() && $photo !== null) {

        $fileName = md5($photo->baseName.time()) . '.' . $photo->extension;
        //$fileName = $photo->baseName . '.' . $photo->extension;
        if($photo->saveAs($path.$fileName)){
          return $fileName;
        }
    }
    return $model->isNewRecord ? false : $model->getOldAttribute($attribute);
}

public function getUploadPath(){
  return Yii::getAlias('@webroot').'/'.$this->upload_foler.'/';
}

public function getUploadUrl(){
  return Yii::getAlias('@web').'/'.$this->upload_foler.'/';
}

public function getPhotoViewer(){
  return empty($this->photo) ? Yii::getAlias('@web').'/img/none.png' : $this->getUploadUrl().$this->photo;
}
// ...

}

<?php $form = ActiveForm::begin([
    'options' => ['enctype' => 'multipart/form-data']
  ]); ?>

  <?= $form->field($model, 'photo')->fileInput() ?>

<?php
use yii\helpers\Html;
use yii\widgets\ActiveForm;
?>
<div class="easy-upload-form">
  <?php $form = ActiveForm::begin([
      'options' => ['enctype' => 'multipart/form-data']
    ]); ?>
    <?= $form->field($model, 'name')->textInput(['maxlength' => true]) ?>
    <?= $form->field($model, 'surname')->textInput(['maxlength' => true]) ?>
    <div class="row">
      <div class="col-md-2">
        <div class="well text-center">
          <?= Html::img($model->getPhotoViewer(),['style'=>'width:100px;','class'=>'img-rounded']); ?>
        </div>
      </div>
      <div class="col-md-10">
            <?= $form->field($model, 'photo')->fileInput() ?>
      </div>
    </div>
    <div class="form-group">
        <?= Html::submitButton($model->isNewRecord ? Yii::t('app', 'Create') : Yii::t('app', 'Update'), ['class' => $model->isNewRecord ? 'btn btn-success' : 'btn btn-primary']) ?>
    </div>

    <?php ActiveForm::end(); ?>

</div>

<?php

// ....

public function actionCreate()
{
    $model = new EasyUpload();

    if ($model->load(Yii::$app->request->post()) && $model->validate()) {
        $model->photo = $model->upload($model,'photo');
        $model->save();
        return $this->redirect(['view', 'id' => $model->id]);
    } else {
        return $this->render('create', [
            'model' => $model,
        ]);
    }
}


public function actionUpdate($id)
{
    $model = $this->findModel($id);

    if ($model->load(Yii::$app->request->post()) && $model->validate()) {
        $model->photo = $model->upload($model,'photo');
        $model->save();
        return $this->redirect(['view', 'id' => $model->id]);
    }  else {
        return $this->render('update', [
            'model' => $model,
        ]);
    }
}

<?= GridView::widget([
    'dataProvider' => $dataProvider,
    'filterModel' => $searchModel,
    'columns' => [
        //['class' => 'yii\grid\SerialColumn'],
        [
            'options'=>['style'=>'width:150px;'],
            'format'=>'raw',
            'attribute'=>'photo',
            'value'=>function($model){
              return Html::tag('div','',[
                'style'=>'width:150px;height:95px;
                          border-top: 10px solid rgba(255, 255, 255, .46);
                          background-image:url('.$model->photoViewer.');
                          background-size: cover;
                          background-position:center center;
                          background-repeat:no-repeat;
                          ']);
            }
        ],
        //'id',
        'name',
        'surname',
        // 'photo',
        // 'photos:ntext',

        ['class' => 'yii\grid\ActionColumn'],
    ],
]); ?>

<?= DetailView::widget([
    'model' => $model,
    'attributes' => [
        'id',
        'name',
        'surname',
        //'photoViewer:image',
        [
            'format'=>'raw',
            'attribute'=>'photo',
            'value'=>Html::img($model->photoViewer,['class'=>'img-thumbnail','style'=>'width:200px;'])
        ]
    ],
]) ?>

<?php

//...

    public function rules()
    {
        return [
            [['name', 'surname'], 'required'],
            [['name', 'surname'], 'string', 'max' => 100],
            [['photo'], 'file',
              'skipOnEmpty' => true,
              'extensions' => 'png,jpg'
            ],
            [['photos'], 'file',
              'skipOnEmpty' => true,
              'maxFiles' => 3,
              'extensions' => 'png,jpg'
            ]
        ];
    }

    public function uploadMultiple($model,$attribute)
    {
      $photos  = UploadedFile::getInstances($model, $attribute);
      $path = $this->getUploadPath();
      if ($this->validate() && $photos !== null) {
          $filenames = [];
          foreach ($photos as $file) {
                  $filename = md5($file->baseName.time()) . '.' . $file->extension;
                  if($file->saveAs($path . $filename)){
                    $filenames[] = $filename;
                  }
          }
          if($model->isNewRecord){
            return implode(',', $filenames);
          }else{
            return implode(',',(ArrayHelper::merge($filenames,$model->getOwnPhotosToArray())));
          }
      }

      return $model->isNewRecord ? false : $model->getOldAttribute($attribute);
    }

    public function getPhotosViewer(){
      $photos = $this->photos ? @explode(',',$this->photos) : [];
      $img = '';
      foreach ($photos as  $photo) {
        $img.= ' '.Html::img($this->getUploadUrl().$photo,['class'=>'img-thumbnail','style'=>'max-width:100px;']);
      }
      return $img;
    }

    public function getOwnPhotosToArray()
    {
      return $this->getOldAttribute('photos') ? @explode(',',$this->getOldAttribute('photos')) : [];
    }

<?= $form->field($model, 'photos[]')->fileInput(['multiple' => true]) ?>
<div class="well">
  <?= $model->getPhotosViewer(); ?>
</div>

<?= DetailView::widget([
    'model' => $model,
    'attributes' => [
        'id',
        'name',
        'surname',
        //'photoViewer:image',
        [
            'format'=>'raw',
            'attribute'=>'photo',
            'value'=>Html::img($model->photoViewer,['class'=>'img-thumbnail','style'=>'width:200px;'])
        ],
        [
            'format'=>'raw',
            'attribute'=>'photos',
            'value'=>$model->getPhotosViewer()
        ]
    ],
]) ?>

<?php

//...

public function actionCreate()
{
    $model = new EasyUpload();

    if ($model->load(Yii::$app->request->post()) && $model->validate()) {
        $model->photo = $model->upload($model,'photo');
        $model->photos = $model->uploadMultiple($model,'photos');
        $model->save();
        return $this->redirect(['view', 'id' => $model->id]);
    } else {
        return $this->render('create', [
            'model' => $model,
        ]);
    }
}

public function actionUpdate($id)
{
    $model = $this->findModel($id);

    if ($model->load(Yii::$app->request->post()) && $model->validate()) {
        $model->photo = $model->upload($model,'photo');
        $model->photos = $model->uploadMultiple($model,'photos');
        $model->save();
        return $this->redirect(['view', 'id' => $model->id]);
    }  else {
        return $this->render('update', [
            'model' => $model,
        ]);
    }
}