remix

IE6はShiftJISかUTF8が必須

$filename= "本語ファイル名.tsv";
$filename= mb_convert_encoding( $filename, "UTF8");
$filename= urlencode( $filename );

header( 'Content-Type: application/octet-stream; name="'.$filename.'"' );
header( 'Content-Disposition: attachment; filename="'.$filename.'"' );
header( 'Content-Length: '.filesize( "/test.dat" ) );
header( 'Connection: close' );

@readfile( "/test.dat" );

exit();

確認環境は...