php文件下载

<?php
    //要下载的文件目录
    $file_dir = "upload/";
    //要下载的文件名称
    $file_name = "1.jpg";
    // 打开文件
    $file = fopen($file_dir . $file_name,"r");
    //输入文件标签
    Header("Content-type: application/octet-stream");
    Header("Accept-Ranges: bytes");
    Header("Accept-Length: ".filesize($file_dir . $file_name));
    Header("Content-Disposition: attachment; filename=" . $file_name);
    //输出文件内容
    echo fread($file,filesize($file_dir . $file_name));
    fclose($file);
    exit();
?>