使用 PHP 下载时，文件大小是否有限制？

Question

尝试使用通常的 PHP 强制下载文件：

header("Content-type: $type" );
header("Content-Disposition: attachment; filename=$name");
header('Content-Length: ' . filesize($path));

对于小于 32 mb 的文件，它可以成功下载。对于更大的文件，它只返回归零的文件。

显然存在某种限制，但是什么限制了它呢？使用 Apache 2.2.11 和 PHP 5.3.0。

Answer 1

我最终偶然发现了这篇文章： http://w-shadow.com/blog/2007/08/12/how-to-force-file-download-with-php/。

function output_file($file, $name, $mime_type='')
{
 /*
 This function takes a path to a file to output ($file), 
 the filename that the browser will see ($name) and 
 the MIME type of the file ($mime_type, optional).

 If you want to do something on download abort/finish,
 register_shutdown_function('function_name');
 */
 if(!is_readable($file)) die('File not found or inaccessible!');

 $size = filesize($file);
 $name = rawurldecode($name);

 /* Figure out the MIME type (if not specified) */
 $known_mime_types=array(
    "pdf" => "application/pdf",
    "txt" => "text/plain",
    "html" => "text/html",
    "htm" => "text/html",
    "exe" => "application/octet-stream",
    "zip" => "application/zip",
    "doc" => "application/msword",
    "xls" => "application/vnd.ms-excel",
    "ppt" => "application/vnd.ms-powerpoint",
    "gif" => "image/gif",
    "png" => "image/png",
    "jpeg"=> "image/jpg",
    "jpg" =>  "image/jpg",
    "php" => "text/plain"
 );

 if($mime_type==''){
     $file_extension = strtolower(substr(strrchr($file,"."),1));
     if(array_key_exists($file_extension, $known_mime_types)){
        $mime_type=$known_mime_types[$file_extension];
     } else {
        $mime_type="application/force-download";
     };
 };

 ob_end_clean(); //turn off output buffering to decrease cpu usage

 // required for IE, otherwise Content-Disposition may be ignored
 if(ini_get('zlib.output_compression'))
  ini_set('zlib.output_compression', 'Off');

 header('Content-Type: ' . $mime_type);
 header('Content-Disposition: attachment; filename="'.$name.'"');
 header("Content-Transfer-Encoding: binary");
 header('Accept-Ranges: bytes');

 /* The three lines below basically make the 
    download non-cacheable */
 header("Cache-control: private");
 header('Pragma: private');
 header("Expires: Mon, 26 Jul 1997 05:00:00 GMT");

 // multipart-download and download resuming support
 if(isset($_SERVER['HTTP_RANGE']))
 {
    list($a, $range) = explode("=",$_SERVER['HTTP_RANGE'],2);
    list($range) = explode(",",$range,2);
    list($range, $range_end) = explode("-", $range);
    $range=intval($range);
    if(!$range_end) {
        $range_end=$size-1;
    } else {
        $range_end=intval($range_end);
    }

    $new_length = $range_end-$range+1;
    header("HTTP/1.1 206 Partial Content");
    header("Content-Length: $new_length");
    header("Content-Range: bytes $range-$range_end/$size");
 } else {
    $new_length=$size;
    header("Content-Length: ".$size);
 }

 /* output the file itself */
 $chunksize = 1*(1024*1024); //you may want to change this
 $bytes_send = 0;
 if ($file = fopen($file, 'r'))
 {
    if(isset($_SERVER['HTTP_RANGE']))
    fseek($file, $range);

    while(!feof($file) && 
        (!connection_aborted()) && 
        ($bytes_send<$new_length)
          )
    {
        $buffer = fread($file, $chunksize);
        print($buffer); //echo($buffer); // is also possible
        flush();
        $bytes_send += strlen($buffer);
    }
 fclose($file);
 } else die('Error - can not open file.');

die();
}   

/*********************************************
            Example of use
**********************************************/

/* 
Make sure script execution doesn't time out.
Set maximum execution time in seconds (0 means no limit).
*/
set_time_limit(0);  
$file_path='that_one_file.txt';
output_file($file_path, 'some file.txt', 'text/plain');

添加所有推荐的标题并

 ob_end_clean(); //turn off output buffering to decrease cpu usage

在任何输出之前使用： - 有所帮助。没有更多可观察到的限制。文件下载完全，即使是大文件。

Answer 2

看起来您正在将整个文件加载到 RAM 中，然后再将其发送给收件人。您需要研究 PHP Streams，以便能够发送完整的文件内容，而不必先将其全部读入 RAM： http://php.net/streams

Answer 3

还可能需要set_time_limit(0);

Answer 4

在 php.ini 中您将看到该设置。

我一时记不起选项名称，但我现在会查看 php.ini 并尝试找到它。

只需将其删除即可工作。

添加

好的，如果我错了，请有人纠正我，但是是吗？

内存限制

Answer 5

Apache 中的构建有 1 GB 限制，即使您尝试从根目录下载文件，也完全避免了 php。

Answer 6

花了我很长时间去调试。我认为这可能是 CloudFlare 背后的代理，标头丢失。结果我正在流式传输的文件达到了内存限制。

我做到了

            ini_set('memory_limit', '128M');