php如何修改下载文件名

$file_url = “./本地路径”
 $out_filename = ‘下载后自动保存的名字’;
 if(!file_exists($file_url)) {
 echo "不存在";
 }else{
 header('Accept-Ranges: bytes');
 header('Accept-Length: ' . filesize( $file_url ));
 header('Content-Transfer-Encoding: binary');
 header('Content-type: application/octet-stream');
 header('Content-Disposition: attachment; filename=' . $out_filename);
 header('Content-Type: application/octet-stream; name=' . $out_filename);
 if(is_file($file_url) && is_readable($file_url)){
 $file = fopen($file_url, "r");
 echo fread($file, filesize($file_url));
 fclose($file);
 }

$file_ur = ‘远程文件地址’;
$out_filename='下载后自动保存的文件名';
 $file = @fopen($file_url, "r");
 if($file){
 $content="";
 while(!feof($file)){//测试文件指针是否到了文件结束的位置
 $data=fread($file,1024);
 $content.=$data;
 }
 fclose($file);
 $filesize = strlen($content);
 header('Accept-Ranges: bytes');
 header('Accept-Length: ' . $filesize);
 header('Content-Transfer-Encoding: binary');
 header('Content-type: application/octet-stream');
 header('Content-Disposition: attachment; filename=' . $out_filename);
 header('Content-Type: application/octet-stream; name=' . $out_filename);
 echo $content;
 die(); 
 }else{
 echo "文件不存在";
 }