文件下载方法

第一次这么亲密的接触下载代码：一般都是先找到文件，然后打开文件，然后输出头文件，最后输出文件内容。

（很关键的几处：Header("Content-type，这里根据不同的文件类型，进行相应的选择。header("Content-Disposition: attachment; filename=".$file_name);会提示你进行下载。

 

<?php $file_name = "2.pdf"; $file_dir = "/home/xujie/www/download/"; if(!file_exists($file_dir.$file_name)){ echo "文件不存在"; exit(); }else{ // 打开文件 $file = fopen($file_dir.$file_name,"r"); // 输入文件标签 Header("Content-type:application/pdf"); Header("Accept-Ranges: bytes"); Header("Accept-Length: ".filesize($file_dir.$file_name)); header("Content-Disposition: attachment; filename=".$file_name); // 输出文件内容 $content = fread($file,filesize($file_dir.$file_name)); echo $content; fclose($file); exit; } ?>

 

从上面实现的下载功能来看，可以好好的总结学习下Header的功能：

header -- 发送一个原始 HTTP 标头，在Header前无能有任何输出，否则出错。

void header ( string string [, bool replace [, int http_response_code]] )

可选参数 replace 指明是替换掉前一条类似的标头还是增加一条相同类型的标头。默认为替换，但如果将其设为 FALSE 则可以强制发送多个同类标头。例如:

http://www.kuqin.com/php5_doc/function.header.html

这里讲解了很多关于下载的代码，我拷贝其中一个看看：

 

<?php $fname = $_GET['file']; $fpath = "downloads/$fname"; $fsize = filesize($fpath); $bufsize = 20000; if(isset($_SERVER['HTTP_RANGE'])) //Partial download { if(preg_match("/^bytes=(//d+)-(//d*)$/", $_SERVER['HTTP_RANGE'], $matches)) { //parsing Range header $from = $matches[1]; $to = $matches[2]; if(empty($to)) { $to = $fsize - 1; // -1 because end byte is included //(From HTTP protocol: // 'The last-byte-pos value gives the byte-offset of the last byte in the range; that is, the byte positions specified are inclusive') } $content_size = $to - $from + 1; header("HTTP/1.1 206 Partial Content"); header("Content-Range: $from-$to/$fsize"); header("Content-Length: $content_size"); header("Content-Type: application/force-download"); header("Content-Disposition: attachment; filename=$fname"); header("Content-Transfer-Encoding: binary"); if(file_exists($fpath) && $fh = fopen($fpath, "rb")) { fseek($fh, $from); $cur_pos = ftell($fh); while($cur_pos !== FALSE && ftell($fh) + $bufsize < $to+1) { $buffer = fread($fh, $bufsize); print $buffer; $cur_pos = ftell($fh); } $buffer = fread($fh, $to+1 - $cur_pos); print $buffer; fclose($fh); } else { header("HTTP/1.1 404 Not Found"); exit; } } else { header("HTTP/1.1 500 Internal Server Error"); exit; } } else // Usual download { header("HTTP/1.1 200 OK"); header("Content-Length: $fsize"); header("Content-Type: application/force-download"); header("Content-Disposition: attachment; filename=$fname"); header("Content-Transfer-Encoding: binary"); if(file_exists($fpath) && $fh = fopen($fpath, "rb")){ while($buf = fread($fh, $bufsize)) print $buf; fclose($fh); } else { header("HTTP/1.1 404 Not Found"); } } ?>