php函数只能下载0.JPG图片其余名称的全不行

<?php function down_life($file_name,$file_sub_dir){ $file_name=iconv("UTF-8","GB2312",$file_name); $file_path=$_SERVER[✀DOCUMENT_ROOT✀].$file_sub_dir.$file_name; if(!file_exists($file_path)){ echo"文件不存在"; return; } $fp=fopen($file_name,"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)){ $file_date=fread($fp,$buffer); $file_count+=$buffer; echo $file_date; } fclose($fp); } down_life("jy1.jpg","/picture/");?>