文件上传文件出错为空？为啥？

头部也写了
enctype="multipart/form-data"
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POST提交的

<input type="file" name="userfile">
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public function postFile(){
$time=date('Y-d-m',time());
$uploaddir = '/public/Uploads/file';
$uploadfile = $uploaddir . basename(@$_FILES['userfile']['name']);
echo '<pre>';
if (move_uploaded_file(@$_FILES['userfile']['tmp_name'], $uploadfile)){
echo "Ok";
echo "Upload: " . @$_FILES["userfile"]["name"] . "<br />";
echo "Type: " . @$_FILES["file"]["type"] . "<br />";
echo "Size: " . (@$_FILES["file"]["size"] / 1024) . " Kb<br />";
echo "Stored in: ". @$_FILES["file"]["tmp_name"].$time;
} else {
return json_encode([]);
}
print_r(@$_FILES);
print "</pre>";

}