framework/web/UploadedFile.php
public static function getInstances($model, $attribute)
    {
        $name = Html::getInputName($model, $attribute);
        return static::getInstancesByName($name);
    }
public static function getInstances($model, $attribute)
    {
        $name = Html::getInputName($model, $attribute);
        return static::getInstancesByName($name);
    }
Returns all uploaded files for the given model attribute.
@param \yii\base\Model $model the data model
@param string $attribute the attribute name. The attribute name may contain array indexes
for tabular file uploading, e.g. '[1]file'.
@return UploadedFile[] array of UploadedFile objects.
Empty array is returned if no available file was found for the given attribute.