function fileDown($file_name){
        $file_name = iconv("utf-8","gb2312",$file_name);
        $file_path = "E:/php/down/".$file_name;
        if(!file_exists($file_path)){
            echo "文件不存在";
            return;
        }
        $fp = fopen($file_path,"r");
        $file_size = filesize($file_path);
        Header("Content-type: application/octet-stream");
        Header("Accept-Ranges: bytes");
        Header("Accept-Length: $file_size");
        Header("Content-Disposition: attachment; filename=".$file_name);
        $buffer = 1024;
        $file_count = 0;
        while(!feof($fp) && ($file_size - $file_count>0)){
            $file_data = fread($fp,$buffer);
            $file_count += $buffer;
            echo $file_data;
        }
        fclose($fp);
    }
$file_name="sai.png";
fileDown($file_name);文件能够下载,但是图片打不开。以前能够打开。别的机器访问这个文件也能打开