yii2文件（图片）上传，url保存到数据表

view视图create.php

use yii\helpers\Html;
use yii\bootstrap\ActiveForm;

 $form = ActiveForm::begin([
    'id' => 'upload',
    'enableAjaxValidation' => false,
    'options' => ['enctype' => 'multipart/form-data']
]);
?>

= $form->field($model, 'thumbnail_url')->fileInput(); ?>
= Html::submitButton($model->isNewRecord ? 'Create' : 'Update', ['class' => $model->isNewRecord ? 'btn btn-success' : 'btn btn-primary']) ?>
 ActiveForm::end(); ?>

控制器方法

    public function actionCreate()
    {
        $model = new 数据表model();
        if ($model->load(Yii::$app->request->post())) {
            $image =  UploadedFile::getInstance($model,'数据表存储字段');
            $ext = $image->getExtension();
            $imageName = time().rand(100,999).'.'.$ext;
            $image->saveAs('uploads/'.$imageName);//设置图片的存储位置
            $model->数据表存储字段 = 'http://www.xxx.cn/uploads/'.$imageName;//设置图片的url，可以用_SERVER["HTTP_HOST"]+图片名代替
            $model->save();

           $this->render('create', [
                'model' => $model,

            ]);   
    }

官方权威指南：文件上传，http://www.yiichina.com/doc/guide/2.0/input-file-upload