PHP 关于文件下传上载 断点续传有关问题

PHP 关于文件上传下载 断点续传问题

PHP 关于文件上传下载 断点续传问题

让PHP下载代码支持断点续传 主要靠的 HTTP协议中header? Content-Range来实现

先来说说 HTTP的下载原理

对于HTTP协议，向服务器请求某个文件时，只要发送类似如下的请求即可：

GET /Path/FileName HTTP/1.0
Host:?www.server.com:80
Accept: **表示接收任何类型的数据。User-Agent表示用户代理，这个字段可有可无，但强烈建议加上，因为它是服务器统计、追踪以及识别客户端的依据。Connection字段中的close表示使用非持久连接。

关于HTTP协议更多的细节可以参考RFC2616（HTTP 1.1）。因为我只是想通过HTTP协议实现文件下载，所以也只看了一部分，并没有看全。

如果服务器成功收到该请求，并且没有出现任何错误，则会返回类似下面的数据：

HTTP/1.0 200 OK
Content-Length: 13057672
Content-Type: application/octet-stream
Last-Modified: Wed, 10 Oct 2005 00:56:34 GMT
Accept-Ranges: bytes
ETag: "2f38a6cac7cec51:160c"
Server: Microsoft-IIS/6.0
X-Powered-By: ASP.NET
Date: Wed, 16 Nov 2005 01:57:54 GMT
Connection: close

下面来解释下这些返回信息的含义

第一行是协议名称及版本号，空格后面会有一个三位数的数字，是HTTP协议的响应状态码，200表示成功，OK是对状态码的简短文字描述。状态码共有5类：
1xx属于通知类；
2xx属于成功类；
3xx属于重定向类；
4xx属于客户端错误类；
5xx属于服务端错误类。

对 于状态码，相信大家对404应该很熟悉，如果向一个服务器请求一个不存在的文件，就会得到该错误，通常浏览器也会显示类似“HTTP 404 - 未找到文件”这样的错误。Content-Length字段是一个比较重要的字段，它标明了服务器返回数据的长度，这个长度是不包含HTTP头长度的。换句话说，我们的请求中并没有Range字段（后面会说到），表示我们请求的是整个文件，所以Content-Length就是整个文件的大小。其余各字段是一些关于文件和服务器的属性信息。

以上就是通过HTTP协议实现文件下载的全过程。但还不能实现断点续传，而实际上断点续传的实现非常简单，只要在请求中加一个Range字段就可以了。

假如一个文件有1000个字节，那么其范围就是0-999，则：

Range: bytes=500-??????表示读取该文件的500-999字节，共500字节。
Range: bytes=500-599???表示读取该文件的500-599字节，共100字节。
Range还有其它几种写法，但上面这两种是最常用的，对于断点续传也足矣了。如果HTTP请求中包含Range字段，那么服务器会返回206（Partial Content），同时HTTP头中也会有一个相应的Content-Range字段，类似下面的格式：
Content-Range: bytes 500-999/1000
Content-Range字段说明服务器返回了文件的某个范围及文件的总长度。这时Content-Length字段就不是整个文件的大小了，而是对应文件这个范围的字节数，这一点一定要注意。

下面来看PHP对断点续传支持的演示：

先定义一个函数? getRange() 这个函数用来处理? header中 Range 具体数据的处理

<p>
<span style="line-height: 1.5; color: #008080;"> 1</span> <span style="line-height: 1.5; color: #008000;">/*</span><span style="line-height: 1.5; color: #008000;">* $file_size  文件大小 </span><span style="line-height: 1.5; color: #008000;">*/</span><span style="line-height: 1.5;">
</span><span style="line-height: 1.5; color: #008080;"> 2</span> <span style="line-height: 1.5;">?</span><span style="line-height: 1.5; color: #0000ff;">function</span><span style="line-height: 1.5;"> getRange(</span><span style="line-height: 1.5; color: #800080;">$file_size</span><span style="line-height: 1.5;">){
</span><span style="line-height: 1.5; color: #008080;"> 3</span> <span style="line-height: 1.5;">    </span><span style="line-height: 1.5; color: #800080;">$range</span><span style="line-height: 1.5;"> </span><span style="line-height: 1.5;">=</span><span style="line-height: 1.5;"> </span><span style="line-height: 1.5; color: #0000ff;">isset</span><span style="line-height: 1.5;">(</span><span style="line-height: 1.5; color: #800080;">$_SERVER</span><span style="line-height: 1.5;">[</span><span style="line-height: 1.5;">'</span><span style="line-height: 1.5;">HTTP_RANGE</span><span style="line-height: 1.5;">'</span><span style="line-height: 1.5;">])</span><span style="line-height: 1.5;">?</span><span style="line-height: 1.5; color: #800080;">$_SERVER</span><span style="line-height: 1.5;">[</span><span style="line-height: 1.5;">'</span><span style="line-height: 1.5;">HTTP_RANGE</span><span style="line-height: 1.5;">'</span><span style="line-height: 1.5;">]</span><span style="line-height: 1.5;">:</span><span style="line-height: 1.5; color: #0000ff;">null</span><span style="line-height: 1.5;">;
</span><span style="line-height: 1.5; color: #008080;"> 4</span> <span style="line-height: 1.5;">    </span><span style="line-height: 1.5; color: #0000ff;">if</span><span style="line-height: 1.5;">(</span><span style="line-height: 1.5;">!</span><span style="line-height: 1.5; color: #0000ff;">empty</span><span style="line-height: 1.5;">(</span><span style="line-height: 1.5; color: #800080;">$range</span><span style="line-height: 1.5;">)){
</span><span style="line-height: 1.5; color: #008080;"> 5</span> <span style="line-height: 1.5;">        </span><span style="line-height: 1.5; color: #800080;">$range</span><span style="line-height: 1.5;"> </span><span style="line-height: 1.5;">=</span><span style="line-height: 1.5;"> </span><span style="line-height: 1.5; color: #008080;">preg_replace</span><span style="line-height: 1.5;">(</span><span style="line-height: 1.5;">'</span><span style="line-height: 1.5;">/[\s|,].*/</span><span style="line-height: 1.5;">'</span><span style="line-height: 1.5;">,</span><span style="line-height: 1.5;"> </span><span style="line-height: 1.5;">''</span><span style="line-height: 1.5;">,</span><span style="line-height: 1.5;"> </span><span style="line-height: 1.5; color: #800080;">$range</span><span style="line-height: 1.5;">);
</span><span style="line-height: 1.5; color: #008080;"> 6</span> <span style="line-height: 1.5;">        </span><span style="line-height: 1.5; color: #800080;">$range</span><span style="line-height: 1.5;"> </span><span style="line-height: 1.5;">=</span><span style="line-height: 1.5;"> </span><span style="line-height: 1.5; color: #008080;">explode</span><span style="line-height: 1.5;">(</span><span style="line-height: 1.5;">'</span><span style="line-height: 1.5;">-</span><span style="line-height: 1.5;">'</span><span style="line-height: 1.5;">,</span><span style="line-height: 1.5; color: #008080;">substr</span><span style="line-height: 1.5;">(</span><span style="line-height: 1.5; color: #800080;">$range</span><span style="line-height: 1.5;">,</span><span style="line-height: 1.5;">6</span><span style="line-height: 1.5;">));
</span><span style="line-height: 1.5; color: #008080;"> 7</span> <span style="line-height: 1.5;">        </span><span style="line-height: 1.5; color: #0000ff;">if</span><span style="line-height: 1.5;"> (</span><span style="line-height: 1.5; color: #008080;">count</span><span style="line-height: 1.5;">(</span><span style="line-height: 1.5; color: #800080;">$range</span><span style="line-height: 1.5;">) </span><span style="line-height: 1.5;"><span style="line-height: 1.5;"> </span><span style="line-height: 1.5;">2</span><span style="line-height: 1.5;"> ) {
</span><span style="line-height: 1.5; color: #008080;"> 8</span> <span style="line-height: 1.5;">            </span><span style="line-height: 1.5; color: #800080;">$range</span><span style="line-height: 1.5;">[</span><span style="line-height: 1.5;">1</span><span style="line-height: 1.5;">] </span><span style="line-height: 1.5;">=</span><span style="line-height: 1.5;"> </span><span style="line-height: 1.5; color: #800080;">$file_size</span><span style="line-height: 1.5;">;
</span><span style="line-height: 1.5; color: #008080;"> 9</span> <span style="line-height: 1.5;">        }
</span><span style="line-height: 1.5; color: #008080;">10</span> <span style="line-height: 1.5;">        </span><span style="line-height: 1.5; color: #800080;">$range</span><span style="line-height: 1.5;"> </span><span style="line-height: 1.5;">=</span><span style="line-height: 1.5;"> </span><span style="line-height: 1.5; color: #008080;">array_combine</span><span style="line-height: 1.5;">(</span><span style="line-height: 1.5; color: #0000ff;">array</span><span style="line-height: 1.5;">(</span><span style="line-height: 1.5;">'</span><span style="line-height: 1.5;">start</span><span style="line-height: 1.5;">'</span><span style="line-height: 1.5;">,</span><span style="line-height: 1.5;">'</span><span style="line-height: 1.5;">end</span><span style="line-height: 1.5;">'</span><span style="line-height: 1.5;">)</span><span style="line-height: 1.5;">,</span><span style="line-height: 1.5; color: #800080;">$range</span><span style="line-height: 1.5;">);
</span><span style="line-height: 1.5; color: #008080;">11</span> <span style="line-height: 1.5;">        </span><span style="line-height: 1.5; color: #0000ff;">if</span><span style="line-height: 1.5;"> (</span><span style="line-height: 1.5; color: #0000ff;">empty</span><span style="line-height: 1.5;">(</span><span style="line-height: 1.5; color: #800080;">$range</span><span style="line-height: 1.5;">[</span><span style="line-height: 1.5;">'</span><span style="line-height: 1.5;">start</span><span style="line-height: 1.5;">'</span><span style="line-height: 1.5;">])) {
</span><span style="line-height: 1.5; color: #008080;">12</span> <span style="line-height: 1.5;">            </span><span style="line-height: 1.5; color: #800080;">$range</span><span style="line-height: 1.5;">[</span><span style="line-height: 1.5;">'</span><span style="line-height: 1.5;">start</span><span style="line-height: 1.5;">'</span><span style="line-height: 1.5;">] </span><span style="line-height: 1.5;">=</span><span style="line-height: 1.5;"> </span><span style="line-height: 1.5;">0</span><span style="line-height: 1.5;">;
</span><span style="line-height: 1.5; color: #008080;">13</span> <span style="line-height: 1.5;">        }
</span><span style="line-height: 1.5; color: #008080;">14</span> <span style="line-height: 1.5;">        </span><span style="line-height: 1.5; color: #0000ff;">if</span><span style="line-height: 1.5;"> (</span><span style="line-height: 1.5;">!</span><span style="line-height: 1.5; color: #0000ff;">isset</span><span style="line-height: 1.5;"> (</span><span style="line-height: 1.5; color: #800080;">$range</span><span style="line-height: 1.5;">[</span><span style="line-height: 1.5;">'</span><span style="line-height: 1.5;">end</span><span style="line-height: 1.5;">'</span><span style="line-height: 1.5;">]) </span><span style="line-height: 1.5;">||</span><span style="line-height: 1.5;"> </span><span style="line-height: 1.5; color: #0000ff;">empty</span><span style="line-height: 1.5;">(</span><span style="line-height: 1.5; color: #800080;">$range</span><span style="line-height: 1.5;">[</span><span style="line-height: 1.5;">'</span><span style="line-height: 1.5;">end</span><span style="line-height: 1.5;">'</span><span style="line-height: 1.5;">])) {
</span><span style="line-height: 1.5; color: #008080;">15</span> <span style="line-height: 1.5;">            </span><span style="line-height: 1.5; color: #800080;">$range</span><span style="line-height: 1.5;">[</span><span style="line-height: 1.5;">'</span><span style="line-height: 1.5;">end</span><span style="line-height: 1.5;">'</span><span style="line-height: 1.5;">] </span><span style="line-height: 1.5;">=</span><span style="line-height: 1.5;"> </span><span style="line-height: 1.5; color: #800080;">$file_size</span><span style="line-height: 1.5;">;
</span><span style="line-height: 1.5; color: #008080;">16</span> <span style="line-height: 1.5;">        }
</span><span style="line-height: 1.5; color: #008080;">17</span> <span style="line-height: 1.5;">        </span><span style="line-height: 1.5; color: #0000ff;">return</span><span style="line-height: 1.5;"> </span><span style="line-height: 1.5; color: #800080;">$range</span><span style="line-height: 1.5;">;
</span><span style="line-height: 1.5; color: #008080;">18</span> <span style="line-height: 1.5;">    }
</span><span style="line-height: 1.5; color: #008080;">19</span> <span style="line-height: 1.5;">    </span><span style="line-height: 1.5; color: #0000ff;">return</span><span style="line-height: 1.5;"> </span><span style="line-height: 1.5; color: #0000ff;">null</span><span style="line-height: 1.5;">;
</span><span style="line-height: 1.5; color: #008080;">20</span> <span style="line-height: 1.5;">}</span>
</span></p>

假设文件的地址为 $file_path

<p>
<span style="line-height: 1.5; color: #008080;"> 1</span> <span style="line-height: 1.5; color: #800080;">$speed</span><span style="line-height: 1.5;"> </span><span style="line-height: 1.5;">=</span><span style="line-height: 1.5;"> </span><span style="line-height: 1.5;">512</span><span style="line-height: 1.5;">;</span><span style="line-height: 1.5; color: #008000;">//</span><span style="line-height: 1.5; color: #008000;">此参数为下载最大速度</span><span style="line-height: 1.5; color: #008000;">
</span><span style="line-height: 1.5; color: #008080;"> 2</span> <span style="line-height: 1.5; color: #008000;">?</span><span style="line-height: 1.5; color: #800080;">$pos</span><span style="line-height: 1.5;"> </span><span style="line-height: 1.5;">=</span><span style="line-height: 1.5;"> </span><span style="line-height: 1.5; color: #008080;">strrpos</span><span style="line-height: 1.5;">(</span><span style="line-height: 1.5; color: #800080;">$file_path</span><span style="line-height: 1.5;">,</span><span style="line-height: 1.5;"> </span><span style="line-height: 1.5;">"</span><span style="line-height: 1.5;">/</span><span style="line-height: 1.5;">"</span><span style="line-height: 1.5;">);
</span><span style="line-height: 1.5; color: #008080;"> 3</span> <span style="line-height: 1.5;">?</span><span style="line-height: 1.5; color: #800080;">$file_name</span><span style="line-height: 1.5;"> </span><span style="line-height: 1.5;">=</span><span style="line-height: 1.5;"> </span><span style="line-height: 1.5; color: #008080;">substr</span><span style="line-height: 1.5;">(</span><span style="line-height: 1.5; color: #800080;">$file_path</span><span style="line-height: 1.5;">,</span><span style="line-height: 1.5;"> </span><span style="line-height: 1.5; color: #800080;">$pos</span><span style="line-height: 1.5;">+</span><span style="line-height: 1.5;">1</span><span style="line-height: 1.5;">);
</span><span style="line-height: 1.5; color: #008080;"> 4</span> <span style="line-height: 1.5; color: #800080;">$file_size</span><span style="line-height: 1.5;"> </span><span style="line-height: 1.5;">=</span><span style="line-height: 1.5;"> </span><span style="line-height: 1.5; color: #008080;">filesize</span><span style="line-height: 1.5;">(</span><span style="line-height: 1.5; color: #800080;">$file_path</span><span style="line-height: 1.5;">);
</span><span style="line-height: 1.5; color: #008080;"> 5</span> <span style="line-height: 1.5; color: #800080;">$ranges</span><span style="line-height: 1.5;"> </span><span style="line-height: 1.5;">=</span><span style="line-height: 1.5;"> getRange(</span><span style="line-height: 1.5; color: #800080;">$file_size</span><span style="line-height: 1.5;">);
</span><span style="line-height: 1.5; color: #008080;"> 6</span> <span style="line-height: 1.5; color: #800080;">$fh</span><span style="line-height: 1.5;"> </span><span style="line-height: 1.5;">=</span><span style="line-height: 1.5;">  </span><span style="line-height: 1.5; color: #008080;">fopen</span><span style="line-height: 1.5;">(</span><span style="line-height: 1.5; color: #800080;">$file_path</span><span style="line-height: 1.5;">,</span><span style="line-height: 1.5;"> </span><span style="line-height: 1.5;">"</span><span style="line-height: 1.5;">rb</span><span style="line-height: 1.5;">"</span><span style="line-height: 1.5;">);
</span><span style="line-height: 1.5; color: #008080;"> 7</span> <span style="line-height: 1.5; color: #008080;">header</span><span style="line-height: 1.5;">(</span><span style="line-height: 1.5;">'</span><span style="line-height: 1.5;">Cache-control: public</span><span style="line-height: 1.5;">'</span><span style="line-height: 1.5;">);
</span><span style="line-height: 1.5; color: #008080;"> 8</span> <span style="line-height: 1.5; color: #008080;">header</span><span style="line-height: 1.5;">(</span><span style="line-height: 1.5;">'</span><span style="line-height: 1.5;">Content-Type: application/octet-stream</span><span style="line-height: 1.5;">'</span><span style="line-height: 1.5;">);
</span><span style="line-height: 1.5; color: #008080;"> 9</span> <span style="line-height: 1.5; color: #008080;">header</span><span style="line-height: 1.5;">(</span><span style="line-height: 1.5;">'</span><span style="line-height: 1.5;">Content-Disposition: attachment; filename=</span><span style="line-height: 1.5;">'</span><span style="line-height: 1.5;">.</span><span style="line-height: 1.5; color: #800080;">$file_name</span><span style="line-height: 1.5;">);
</span><span style="line-height: 1.5; color: #008080;">10</span> <span style="line-height: 1.5; color: #0000ff;">if</span><span style="line-height: 1.5;"> (</span><span style="line-height: 1.5; color: #800080;">$ranges</span><span style="line-height: 1.5;"> </span><span style="line-height: 1.5;">!=</span><span style="line-height: 1.5;"> </span><span style="line-height: 1.5; color: #0000ff;">null</span><span style="line-height: 1.5;">) {
</span><span style="line-height: 1.5; color: #008080;">11</span> <span style="line-height: 1.5;">    </span><span style="line-height: 1.5; color: #008080;">header</span><span style="line-height: 1.5;">(</span><span style="line-height: 1.5;">'</span><span style="line-height: 1.5;">HTTP/1.1 206 Partial Content</span><span style="line-height: 1.5;">'</span><span style="line-height: 1.5;">);
</span><span style="line-height: 1.5; color: #008080;">12</span> <span style="line-height: 1.5;">    </span><span style="line-height: 1.5; color: #008080;">header</span><span style="line-height: 1.5;">(</span><span style="line-height: 1.5;">'</span><span style="line-height: 1.5;">Accept-Ranges: bytes</span><span style="line-height: 1.5;">'</span><span style="line-height: 1.5;">);
</span><span style="line-height: 1.5; color: #008080;">13</span> <span style="line-height: 1.5;">    </span><span style="line-height: 1.5; color: #008080;">header</span><span style="line-height: 1.5;">(</span><span style="line-height: 1.5; color: #008080;">sprintf</span><span style="line-height: 1.5;">(</span><span style="line-height: 1.5;">'</span><span style="line-height: 1.5;">Content-Length: %u</span><span style="line-height: 1.5;">'</span><span style="line-height: 1.5;">,</span><span style="line-height: 1.5; color: #800080;">$ranges</span><span style="line-height: 1.5;">[</span><span style="line-height: 1.5;">'</span><span style="line-height: 1.5;">end</span><span style="line-height: 1.5;">'</span><span style="line-height: 1.5;">] </span><span style="line-height: 1.5;">-</span><span style="line-height: 1.5;"> </span><span style="line-height: 1.5; color: #800080;">$ranges</span><span style="line-height: 1.5;">[</span><span style="line-height: 1.5;">'</span><span style="line-height: 1.5;">start</span><span style="line-height: 1.5;">'</span><span style="line-height: 1.5;">]));
</span><span style="line-height: 1.5; color: #008080;">14</span> <span style="line-height: 1.5;">    </span><span style="line-height: 1.5; color: #008080;">header</span><span style="line-height: 1.5;">(</span><span style="line-height: 1.5; color: #008080;">sprintf</span><span style="line-height: 1.5;">(</span><span style="line-height: 1.5;">'</span><span style="line-height: 1.5;">Content-Range: bytes %s-%s/%s</span><span style="line-height: 1.5;">'</span><span style="line-height: 1.5;">,</span><span style="line-height: 1.5;"> </span><span style="line-height: 1.5; color: #800080;">$ranges</span><span style="line-height: 1.5;">[</span><span style="line-height: 1.5;">'</span><span style="line-height: 1.5;">start</span><span style="line-height: 1.5;">'</span><span style="line-height: 1.5;">]</span><span style="line-height: 1.5;">,</span><span style="line-height: 1.5;"> </span><span style="line-height: 1.5; color: #800080;">$ranges</span><span style="line-height: 1.5;">[</span><span style="line-height: 1.5;">'</span><span style="line-height: 1.5;">end</span><span style="line-height: 1.5;">'</span><span style="line-height: 1.5;">]</span><span style="line-height: 1.5;">,</span><span style="line-height: 1.5;"> </span><span style="line-height: 1.5; color: #800080;">$file_size</span><span style="line-height: 1.5;">));
</span><span style="line-height: 1.5; color: #008080;">15</span> <span style="line-height: 1.5;">    </span><span style="line-height: 1.5; color: #008080;">fseek</span><span style="line-height: 1.5;">(</span><span style="line-height: 1.5; color: #800080;">$fh</span><span style="line-height: 1.5;">,</span><span style="line-height: 1.5;"> </span><span style="line-height: 1.5; color: #008080;">sprintf</span><span style="line-height: 1.5;">(</span><span style="line-height: 1.5;">'</span><span style="line-height: 1.5;">%u</span><span style="line-height: 1.5;">'</span><span style="line-height: 1.5;">,</span><span style="line-height: 1.5; color: #800080;">$ranges</span><span style="line-height: 1.5;">[</span><span style="line-height: 1.5;">'</span><span style="line-height: 1.5;">start</span><span style="line-height: 1.5;">'</span><span style="line-height: 1.5;">]));
</span><span style="line-height: 1.5; color: #008080;">16</span> <span style="line-height: 1.5;">}</span><span style="line-height: 1.5; color: #0000ff;">else</span><span style="line-height: 1.5;">{
</span><span style="line-height: 1.5; color: #008080;">17</span> <span style="line-height: 1.5;">    </span><span style="line-height: 1.5; color: #008080;">header</span><span style="line-height: 1.5;">(</span><span style="line-height: 1.5;">"</span><span style="line-height: 1.5;">HTTP/1.1 200 OK</span><span style="line-height: 1.5;">"</span><span style="line-height: 1.5;">);
</span><span style="line-height: 1.5; color: #008080;">18</span> <span style="line-height: 1.5;">    </span><span style="line-height: 1.5; color: #008080;">header</span><span style="line-height: 1.5;">(</span><span style="line-height: 1.5; color: #008080;">sprintf</span><span style="line-height: 1.5;">(</span><span style="line-height: 1.5;">'</span><span style="line-height: 1.5;">Content-Length: %s</span><span style="line-height: 1.5;">'</span><span style="line-height: 1.5;">,</span><span style="line-height: 1.5;"> </span><span style="line-height: 1.5; color: #800080;">$file_size</span><span style="line-height: 1.5;">));
</span><span style="line-height: 1.5; color: #008080;">19</span> <span style="line-height: 1.5;">}
</span><span style="line-height: 1.5; color: #008080;">20</span> <span style="line-height: 1.5; color: #0000ff;">while</span><span style="line-height: 1.5;">(</span><span style="line-height: 1.5;">!</span><span style="line-height: 1.5; color: #008080;">feof</span><span style="line-height: 1.5;">(</span><span style="line-height: 1.5; color: #800080;">$fh</span><span style="line-height: 1.5;">))
</span><span style="line-height: 1.5; color: #008080;">21</span> <span style="line-height: 1.5;">{
</span><span style="line-height: 1.5; color: #008080;">22</span> <span style="line-height: 1.5;">    </span><span style="line-height: 1.5; color: #0000ff;">echo</span><span style="line-height: 1.5;">  </span><span style="line-height: 1.5; color: #008080;">fread</span><span style="line-height: 1.5;">(</span><span style="line-height: 1.5; color: #800080;">$fh</span><span style="line-height: 1.5;">,</span><span style="line-height: 1.5;"> </span><span style="line-height: 1.5; color: #008080;">round</span><span style="line-height: 1.5;">(</span><span style="line-height: 1.5; color: #800080;">$speed</span><span style="line-height: 1.5;">*</span><span style="line-height: 1.5;">1024</span><span style="line-height: 1.5;">,</span><span style="line-height: 1.5;"> </span><span style="line-height: 1.5;">0</span><span style="line-height: 1.5;">));
</span><span style="line-height: 1.5; color: #008080;">23</span> <span style="line-height: 1.5;">    </span><span style="line-height: 1.5; color: #008080;">ob_flush</span><span style="line-height: 1.5;">();
</span><span style="line-height: 1.5; color: #008080;">24</span> <span style="line-height: 1.5;">    </span><span style="line-height: 1.5; color: #008080;">sleep</span><span style="line-height: 1.5;">(</span><span style="line-height: 1.5;">1</span><span style="line-height: 1.5;">);
</span><span style="line-height: 1.5; color: #008080;">25</span> <span style="line-height: 1.5;">}
</span><span style="line-height: 1.5; color: #008080;">26</span> <span style="line-height: 1.5;">(</span><span style="line-height: 1.5; color: #800080;">$fh</span><span style="line-height: 1.5;"> </span><span style="line-height: 1.5;">!=</span><span style="line-height: 1.5;"> </span><span style="line-height: 1.5; color: #0000ff;">null</span><span style="line-height: 1.5;">) </span><span style="line-height: 1.5;">&&</span><span style="line-height: 1.5;"> </span><span style="line-height: 1.5; color: #008080;">fclose</span><span style="line-height: 1.5;">(</span><span style="line-height: 1.5; color: #800080;">$fh</span><span style="line-height: 1.5;">);</span>
</p>

基本如此 就可以解决一般性文件的断点续传或者下载了