尝试以下代码：

注意：请确保您的上传文件文件夹具有写权限。

Try below code:
Note: Make sure your uploads folder have write permission.

<?php
define("DOC_ROOT", $_SERVER['DOCUMENT_ROOT']."/");
define("PDF_UPLOADS", DOC_ROOT."uploads/");

$name = $_FILES['file']['name'];
$size = $_FILES['file']['size'];
$type = $_FILES['file']['type'];
$tmp_name = $_FILES['file']['tmp_name'];

if (isset($name)) 
{
    if (!empty($name)) 
    {
        if(move_uploaded_file($tmp_name, PDF_UPLOADS. $name))
            echo 'Uploaded';
        else
            echo "Not Uploaded";
    }
    else 
    {
        echo 'Please choose a file';
    }

}
?>