文件下载的 HTTP 标头

Update: I followed this guide here to build a more robust process for file downloads (http://w-shadow.com/blog/2007/08/12/how-to-force-file-download-with-php/), but there is a significant delay between when the script is executed and when the browser's download dialog appears. Can anyone identify the bottleneck that is causing this?

这是我的实现:

/**
 * Outputs the specified file to the browser.
 *
 * @param string $filePath the path to the file to output
 * @param string $fileName the name of the file
 * @param string $mimeType the type of file
 */
function outputFile($filePath, $fileName, $mimeType = '') {
    // Setup
    $mimeTypes = array(
        'pdf' => 'application/pdf',
        'txt' => 'text/plain',
        'html' => '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'
    );
    
    $fileSize = filesize($filePath);
    $fileName = rawurldecode($fileName);
    $fileExt = '';
    
    // Determine MIME Type
    if($mimeType == '') {
        $fileExt = strtolower(substr(strrchr($filePath, '.'), 1));
        
        if(array_key_exists($fileExt, $mimeTypes)) {
            $mimeType = $mimeTypes[$fileExt];
        }
        else {
            $mimeType = 'application/force-download';
        }
    }
    
    // Disable Output Buffering
    @ob_end_clean();
    
    // IE Required
    if(ini_get('zlib.output_compression')) {
        ini_set('zlib.output_compression', 'Off');
    }
    
    // Send Headers
    header('Content-Type: ' . $mimeType);
    header('Content-Disposition: attachment; filename="' . $fileName . '"');
    header('Content-Transfer-Encoding: binary');
    header('Accept-Ranges: bytes');
    
    // Send Headers: Prevent Caching of File
    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, $rangeEnd) = explode('-', $range);
        
        $range = intval($range);
        
        if(!$rangeEnd) {
            $rangeEnd = $fileSize - 1;
        }
        else {
            $rangeEnd = intval($rangeEnd);
        }
        
        $newLength = $rangeEnd - $range + 1;
        
        // Send Headers
        header('HTTP/1.1 206 Partial Content');
        header('Content-Length: ' . $newLength);
        header('Content-Range: bytes ' . $range - $rangeEnd / $fileSize);
    }
    else {
        $newLength = $fileSize;
        header('Content-Length: ' . $fileSize);
    }
    
    // Output File
    $chunkSize = 1 * (1024*1024);
    $bytesSend = 0;
    
    if($file = fopen($filePath, 'r')) {
        if(isset($_SERVER['HTTP_RANGE'])) {
            fseek($file, $range);
            
            while(!feof($file) && !connection_aborted() && $bytesSend < $newLength) {
                $buffer = fread($file, $chunkSize);
                echo $buffer;
                flush();
                $bytesSend += strlen($buffer);
            }
            
            fclose($file);
        }
    }
}

推荐答案

根据 RFC 2046(多用途 Internet 邮件扩展):

推荐的操作接收
的实现应用程序/八位字节流"实体是简单地提出将数据放入一个文件