HTTP分片下载文件代码

function download($sourceFile, $outFile = '') {
        
    
        //Begin writing headers
        header("Cache-Control:");
        header("Cache-Control: public");

        //设置输出浏览器格式
        header("Content-Type: application/force-download");
        header("Content-Disposition: attachment; filename=" . $outFile);
        header("Accept-Ranges: bytes");

        header("Content-Type: application/force-download");
        header("Cache-Control:");
        header("Cache-Control: public");
        header("Content-Disposition: attachment; filename=" . $outFile);
        header("Accept-Ranges: bytes");
        $size = filesize($sourceFile);
    
        //如果有$_SERVER['HTTP_RANGE']参数
        $httprange = $_SERVER['HTTP_RANGE'];
        if (!$httprange) {
            // 断点后再次连接 $_SERVER['HTTP_RANGE'] 的值 bytes=4390912-
            list ($a, $range) = explode("=", $_SERVER['HTTP_RANGE']);
            //if yes, download missing part
 
            $size2 = $size ; //文件总字节数
 
            $new_length = $size2 - $range; //获取下次下载的长度
            header("HTTP/1.1 206 Partial Content");
            header("Content-Length: $new_length"); //输入总长
            header("Content-Range: bytes {$range}-{$size2}/{$size}"); //Content-Range: bytes 4908618-4988927/4988928 95%的时候
        } else {
            //第一次连接
            $size2 = $size - 1;
            header("Content-Range: bytes 0-{$size2}/{$size}"); //Content-Range: bytes 0-4988927/4988928
            header("Content-Length: " . $size); //输出总长
        }
        //打开文件
        $fp = fopen("{$sourceFile}", "rb");
        //设置指针位置
        fseek($fp, $range);
        //虚幻输出  
        ob_clean(); 
        while (!feof($fp)) {
            //设置文件最长执行时间
            set_time_limit(0);
            print (fread($fp, 1024 * 1)); //输出文件
            flush(); //输出缓冲
            ob_flush();
        }
        fclose($fp);     
        return true;
    }