PHP实现文件下载

<?php
    $FilePath = 'abc.txt';
    $file = fopen("php://output", 'w');

    Header("Content-type: application/octet-stream");
    Header("Accept-Ranges: bytes");
    Header("Accept-Length: ".filesize('abc.txt'));
    Header("Content-Disposition: attachment; filename=".'abc.txt');
    echo fread($file, filesize($FilePath));
    fclose($file);