php文件下载（解决文件下载后多几个字节的问题） 与封装成类的例子

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     class FileDown {

           public $fileName;

           public $fileSize;

               //转码 gb2312         

                  function __construct($fileName){

                      $this->fileName=iconv("utf-8","gb2312",$fileName);

                  }

           function Down (){

               //$_SERVER[‘DOCUMENT_ROOT‘]当前运行脚本所在的文档根目录。在服务器配置文件中定义。

              $path=$_SERVER[‘DOCUMENT_ROOT‘]."/12/".$this->fileName;

              if(!file_exists($path)){

                  die("文件不存在");

                  }          

                $fp=fopen($path,"r");   //读入

            $this->fileSize=filesize($path); 

                  //返回文件的头 浏览器靠头识别下载  //返回

                  //返回的文件类型 流 可以是文本 二进制

                      header("Content-type: application/octet-stream");

                      //按照字节大小返回

                      header("Accept-Ranges: bytes");

                      //返回文件大小

                      header("Accept-Length: $this->fileSize");

                      //这里客户端的弹出对话框，对应的文件名

                      header("Content-Disposition: attachment; filename=".$this->fileName);                     

                    $count=0;

                   $buffer=1024;

                   while(!feof($fp)&& $this->fileSize-$count>0){

                               $fileData=fread($fp,$buffer);

                               $count+=$buffer;

                               echo $fileData;

                       }   

                  fclose($fp);

            }

               }      

    $fd=new FileDown("白羊座.png");

     $fd->Down ();