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文件上传
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============
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在Yii里上传文件通常使用[[yii\web\UploadedFile]]类,
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它把每个上传的文件封装成 `UploadedFile` 对象。
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结合[[yii\widgets\ActiveForm]]和[models](structure-models.md),你可以轻松实现安全的上传文件机制。
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##创建模型 <span id="creating-models"></span>
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和普通的文本输入框类似,当要上传一个文件时,你需要创建一个模型类并且用其中的某个属性来接收上传的文件实例。
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你还需要声明一条验证规则以验证上传的文件。
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举例来讲,
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```php
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namespace app\models;
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use yii\base\Model;
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use yii\web\UploadedFile;
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class UploadForm extends Model
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{
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/**
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* @var UploadedFile
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*/
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public $imageFile;
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public function rules()
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{
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return [
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[['imageFile'], 'file', 'skipOnEmpty' => false, 'extensions' => 'png, jpg'],
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];
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}
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public function upload()
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{
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if ($this->validate()) {
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$this->imageFile->saveAs('uploads/' . $this->imageFile->baseName . '.' . $this->imageFile->extension);
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return true;
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} else {
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return false;
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}
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}
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}
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```
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在以上代码里,`imageFile` 属性用于接收上传的文件实例。它对应一条`file` 验证规则,
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该规则使用 [[yii\validators\FileValidator]] 来确保只上传扩展名为 `png` 或 `jpg` 的文件。
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`upload()` 方法会执行该验证并且把上传的文件保存在服务器上。
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通过 `file` 验证器,你可以检查文件的扩展名,大小,MIME类型等等。详情请查阅
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[Core Validatators](tutorial-core-validators.md#file) 章节。
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>提示: 如果你要上传的是一张图片,可以考虑使用`image`验证器。
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`image` 验证器是通过[[yii\validators\ImageValidator]]实现验证的,确保对应的模型属性
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收到的文件是有效的图片文件,然后才保存,或者使用扩展类[Imagine Extension](https://github.com/yiisoft/yii2-imagine)进行处理.
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##渲染文件输入 <span id="rendering-file-input"></span>
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接下来,在视图里创建一个文件输入控件
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```php
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<?php
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use yii\widgets\ActiveForm;
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?>
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<?php $form = ActiveForm::begin(['options' => ['enctype' => 'multipart/form-data']]) ?>
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<?= $form->field($model, 'imageFile')->fileInput() ?>
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<button>Submit</button>
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<?php ActiveForm::end() ?>
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```
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需要注意的是要记得在表单选项里加入 `enctype` 属性以确保文件能被正常上传。
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`fileInput()` 方法会渲染一个 `<input type="file">` 标签,让用户可以选择一个文件上传。
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> Tip: since version 2.0.8, [[yii\web\widgets\ActiveField::fileInput|fileInput]] adds `enctype` option to the form
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automatically when file input field is used.
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## 视图和模型的连接 <span id="wiring-up"></span>
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现在,在控制器方法里编写连接模型和视图的代码以实现文件上传。
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```php
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namespace app\controllers;
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use Yii;
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use yii\web\Controller;
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use app\models\UploadForm;
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use yii\web\UploadedFile;
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class SiteController extends Controller
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{
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public function actionUpload()
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{
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$model = new UploadForm();
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if (Yii::$app->request->isPost) {
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$model->imageFile = UploadedFile::getInstance($model, 'imageFile');
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if ($model->upload()) {
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// 文件上传成功
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return;
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}
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}
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return $this->render('upload', ['model' => $model]);
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}
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}
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```
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在上面的代码里,当提交表单的时候,[[yii\web\UploadedFile::getInstance()]]方法就被调用,
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上传的文件用一个 `UploadedFile` 实例表示。然后,我们依靠模型的验证规则确保上传的文件是有效的,
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并将文件保存在服务器上。
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## 上传多个文件 <span id="uploading-multiple-files"></span>
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将前面所述的代码做一些调整,也可以一次性上传多个文件。
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首先你得调整模型类,在 `file` 验证规则里增加一个 `maxFiles` 选项,用以限制一次上传文件的最大数量。
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`upload()`方法也得修改,以便一个一个地保存上传的文件。Setting `maxFiles` to `0` means there is no limit on the number of files
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that can be uploaded simultaneously. The maximum number of files allowed to be uploaded simultaneously is also limited
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with PHP directive [`max_file_uploads`](http://php.net/manual/en/ini.core.php#ini.max-file-uploads),
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which defaults to 20. The `upload()` method should also be updated to save the uploaded files one by one.
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```php
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namespace app\models;
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use yii\base\Model;
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use yii\web\UploadedFile;
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class UploadForm extends Model
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{
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/**
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* @var UploadedFile[]
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*/
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public $imageFiles;
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public function rules()
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{
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return [
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[['imageFiles'], 'file', 'skipOnEmpty' => false, 'extensions' => 'png, jpg', 'maxFiles' => 4],
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];
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}
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public function upload()
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{
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if ($this->validate()) {
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foreach ($this->imageFiles as $file) {
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$file->saveAs('uploads/' . $file->baseName . '.' . $file->extension);
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}
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return true;
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} else {
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return false;
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}
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}
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}
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```
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在视图文件里,你需要把 `multiple` 选项添加到`fileInput()`函数调用里,
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这样文件输入控件就可以接收多个文件。
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```php
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<?php
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use yii\widgets\ActiveForm;
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?>
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<?php $form = ActiveForm::begin(['options' => ['enctype' => 'multipart/form-data']]) ?>
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<?= $form->field($model, 'imageFiles[]')->fileInput(['multiple' => true, 'accept' => 'image/*']) ?>
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<button>Submit</button>
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<?php ActiveForm::end() ?>
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```
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最后,在控制器的 action 方法中,你应该调用 `UploadedFile::getInstances()` 而不是 `UploadedFile::getInstance()` 来把
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`UploadedFile` 实例数组赋值给 `UploadForm::imageFiles`。
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```php
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namespace app\controllers;
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use Yii;
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use yii\web\Controller;
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use app\models\UploadForm;
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use yii\web\UploadedFile;
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class SiteController extends Controller
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{
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public function actionUpload()
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{
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$model = new UploadForm();
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if (Yii::$app->request->isPost) {
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$model->imageFiles = UploadedFile::getInstances($model, 'imageFiles');
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if ($model->upload()) {
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// 文件上传成功
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return;
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}
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}
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return $this->render('upload', ['model' => $model]);
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}
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}
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```
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