php 读取文件 更改文件名后提供下载

$filename = dirname(__FILE__) . '/oldfilename.exe';
$out_filename = 'newfilename.exe';
if()) {
echo 'Not Found' . $filename;
exit;
} else {
// We'll be outputting a file
@header('Accept-Ranges: bytes');
@header('Accept-Length: ' . filesize($filename));
// It will be called
@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);
// The source is in filename
$file = @fopen($filename, "r");
echo @fread($file, @filesize($filename));
@fclose($file);
exit;
}