php文件下载封装成一个类 老是多出3个字节，请教错哪了

<br />     class FileDown {<br />    	   public $fileName;<br />    	   public $fileSize;<br />    	   	//转码 gb2312  	   <br />		  		function __construct($fileName){<br />		  			$this->fileName=iconv("utf-8","gb2312",$fileName);<br />		  		}<br />    	   function Down (){<br />    	   	//$_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。<br />    	  	$path=$_SERVER['DOCUMENT_ROOT']."/12/".$this->fileName;<br />    	  	if(!file_exists($path)){<br />    	  		die("文件不存在");<br />    	  		}    	  <br />    	    	$fp=fopen($path,"r");   //读入<br />            $this->fileSize=filesize($path); <br />  			    //返回文件的头 浏览器靠头识别下载  //返回<br />  			    //返回的文件类型 流 可以是文本 二进制<br />			  		header("Content-type: application/octet-stream");<br />			  		//按照字节大小返回<br />			  		header("Accept-Ranges: bytes");<br />			  		//返回文件大小<br />			  		header("Accept-Length: $this->fileSize");<br />			  		//这里客户端的弹出对话框，对应的文件名<br />			  		header("Content-Disposition: attachment; filename=".$this->fileName);			  		<br />			 	   $count=0;<br />			  	 $buffer=1024;<br />			  	 while(!feof($fp)&& $this->fileSize-$count>0){<br />			  	 	        $fileData=fread($fp,$buffer);<br />			  	 	        $count+=$buffer;<br />			  	 	        echo $fileData;<br />			  	 	}	<br />  			    fclose($fp);<br />		    }<br />    	   	}   	<br />    $fd=new FileDown("白羊座.png");<br />     $fd->Down ();<br />