如何在仅存储路径的PHP上向mysql上传和下载文件？

我通过在mysql中存储文件路径来上传文件：

if(isset($_FILES['filefield']))
    {
        $file = $_FILES['filefield'];
        $file_name = $file['name'];
        $file_size = $file['size'];
        $file_type = $file['type'];
        $file_tmpname = $file['tmp_name'];  
        $upload_dir = "C:/xampp/htdocs/intranet/www/public/uploads/";
        $ext_str = "gif,jpg,jpeg,mp3,tiff,bmp,doc,docx,ppt,pptx,txt,pdf";
        $allowed_extensions=explode(',',$ext_str);
        $max_file_size = 10485760;
        $ext = substr($file['name'], strrpos($file['name'], '.') + 1);
        if (!in_array($ext, $allowed_extensions))
            echo "only".$ext_str." files allowed to upload";
        if($file['size']>=$max_file_size)
            echo "only the file less than ".$max_file_size."mb  allowed to upload";
        $path = $upload_dir.$file_name;
        if(move_uploaded_file($file_tmpname, $upload_dir.$file_name))
            ORM::factory('files')->uploadFile($teacher_id, $file_name, $file_size, $file_type, $path);
        else
            echo "The file cant moved to target directory.";

    }

然后如何按路径下载此文件？当然，如果我的上传代码是正确的

试试这个

 $file = 'C:/xampp/htdocs/intranet/www/public/uploads/'.$file_name;

if (file_exists($file)) {
    header('Content-Description: File Transfer');
    header('Content-Type: application/octet-stream');
    header('Content-Disposition: attachment; filename='.basename($file));
    header('Content-Transfer-Encoding: binary');
    header('Expires: 0');
    header('Cache-Control: must-revalidate');
    header('Pragma: public');
    header('Content-Length: ' . filesize($file));
    ob_clean();
    flush();
    readfile($file);
    exit;
}