大文件（超过2GB）上的PHP readfile（）过早结束

Question

我有一个下载大文件的下载脚本（通常超过2GB，有时超过10GB）。下载似乎随机失败。

注意：我正在使用iis

 if(ini_get('zlib.output_compression'))
  ini_set('zlib.output_compression', 'Off');
    $filename = 'https://downloadurl.com/SAS9_4W64.zip';
    $head = array_change_key_case(get_headers("https://downloadurl.com/SAS9.3TS132bit.zip", TRUE));

    $extension = fileexten($filename);
    $fakename = 'SAS9.3TS132bitz';
    if(($filename!= false)&&($fakename!=false&& @fopen('https://downloadurl.com/SAS9.3TS132bit.zip','r')==true)){
    $mime = contenttype($extension);
    set_time_limit(0);

header('Accept-Ranges: bytes');
    header("Content-Type:".$mime);
    header('Cache-Control: must-revalidate, post-check=0, pre-check=0');
    header('Cache-Control: private', false);        


    header('Content-Disposition: attachment;filename='.$fakename.'.'.$extension);

    header('Expires: 0'); 
    header("Content-Transfer-Encoding: binary");
ob_clean();
ob_end_clean();
@readfile($filename);
session_write_close();
    }