PHP Readfile()不为我工作，我不知道为什么

我试图让这段代码工作，但由于某种原因，所有的echo都能够输出正确的内容，但标题似乎不想强制下载我的文档。下面是我试图为文件下载构建的文件。设置为输入如下代码:downloader.php?f=13&t=doc，根据用户权限从两个文件夹中的一个下载命名为201-xxx.doc或201-xxx.pdf的文件。

所有的逻辑工作到底部的标题信息。如果我注释掉报头内容类型和报头内容配置，那么它将把文件读入浏览器。其中任何一行都包含在内，它给我一个错误，说"Error 6 (net::ERR_FILE_NOT_FOUND): The file or directory could not be found."

<?php
//ob_start();
if ( !defined('__DIR__') ) define('__DIR__', dirname(__FILE__));
define( "TLOJ_FSROOT", __DIR__ . "/" );
define('WP_USE_THEMES', false);
require('./wp-blog-header.php');
$lessonnumber = $_REQUEST['f'];
$type = $_REQUEST['t'];
    if ( $lessonnumber < '10' ) { $threedigitlesson = '00' . $lessonnumber; }
    elseif ( $lessonnumber < '100' ) { $threedigitlesson = '0' . $lessonnumber; }
    else { $threedigitlesson = $lessonnumber; }
    $filenamestart = "201-" . $threedigitlesson;
    $contenttype = 'application/octet-stream';
    switch ($type) {
        case 'pdf':
            $extension = '.' . $type;
            $contenttype = 'application/pdf';
            break;
        case 'doc':
            $extension = '.' . $type;
            $contenttype = 'application/msword';
            break;
        default:
            $contenttype = '';
            exit("It appears that you are trying to download a file that is not a lesson document. Please contact us if you believe this to be an error.");
    }
$filename = $filenamestart . '.' . $type;
$current_user = wp_get_current_user();
//$siteurl = site_url();
$pathroot = TLOJ_FSROOT;
$download_path = $pathroot . "1hoefl4priaspoafr/";
    if ( current_user_can("access_s2member_ccap_extendedlessons")) { 
        $download_path = $download_path . "ex/";
    } else {
        $download_path = $download_path . "st/";
    }
$file_path = $download_path . $filename;
$tlojmemberlength = tlojunlocklessons();
if ( !is_user_logged_in() ) { exit("Please log in to access the file"); }
if ( !current_user_can("access_s2member_ccap_downloadlessons") ) { exit("You don't have access to download the lessons!"); }
if ( $lessonnumber > $tlojmemberlength ) { exit("It appears you are trying to jump ahead! While I am excited at your enthusiam, let's not rush our study time."); }
if ( ($lessonnumber > '195') && (!current_user_can("access_s2member_ccap_lastweek")) ) { exit("Upgrade now to access the downloads for the five bonus lessons!"); }
// build Final File Name
$extendedmessage = "";
if ( current_user_can("access_s2member_ccap_extendedlessons")) { $extendedmessage = " - Extended"; }
$myfinishedlessonname = "Lesson " . $lessonnumber . $extendedmessage . " -- The Life of Jesus Study" . "." . $type;
//  echo 'Download Path: ' . $download_path . '<br />';
//  echo 'Source/Lesson Number: ' . $lessonnumber . '<br />';
//  echo 'File Name: ' . $filename . '<br />';
//  echo 'File Type: ' . $type . '<br />';
//  echo 'Allowed Lessons: ' . $tlojmemberlength . '<br />';
//  echo 'Final File Name: ' . $myfinishedlessonname . '<br />';
//  echo 'File Path: ' . $file_path . '<br />';
//  echo 'Content Type: ' . $contenttype . '<br />';
//  echo 'File Size: ' . filesize($file_path) . '<br />';
if (headers_sent()) { exit("Sorry but the headers have already been sent."); }
    ob_end_clean();
if (file_exists($file_path)) {
    header('Content-Description: File Transfer');
    header('Content-type: ' . $contenttype);
    header('Content-disposition: attachment; filename="' . $myfinishedlessonname . '"');
    header('Content-Transfer-Encoding: binary');
    header('Expires: 0');
    header('Cache-Control: ');
    header('Pragma: ');
    header('Content-Length: ' . filesize($file_path));
    flush();
    ob_clean();
    readfile($file_path);
    exit;
} else { exit("No file present."); }

?>

请帮助，因为我已经在这一整天，我困惑到没有结束，为什么这不会工作。Filesize()提取正确的长度，因此我知道我正在查看的路径中有一个文件。

(我也是PHP新手，所以如果有什么我错过了，请分享。)

提前感谢!

  $handle = fopen($file_path, 'rb'); 
  $buffer = ''; 
  while (!feof($handle)) { 
    $buffer = fread($handle, 4096); 
    echo $buffer; 
    ob_flush(); 
    flush(); 
  } 
  fclose($handle); 

Content-Type: application/octet-stream
Content-Disposition: attachment; filename="your-file.jpg"