file验证

/* maxFiles代表一次最多传几个，mimeTypes代表上传文件类型 */
[
    'primaryImage', 'file', 'extensions' => ['png', 'jpg', 'gif'],
    'mimeTypes'=>["image/*"], 
    'maxSize' => 1024*1024,'minSize'=>100*1024,
    'maxFiles'=>6,'checkExtensionByMimeType'=>true
],