PHP输出文件头异常

PHP输出文件头错误
本地 nginx 1.09 测试一切正常,上传到服务器 nginx 1.12, 在选择文本输出时就报错
完整代码:

PHP code

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<?php @$id=$_GET['id']?$_GET['id']:'a';
    @$txt=$_GET['txt']?$_GET['txt']:'';

    $trees=array();
    $trees["a"]="苹果";
    $trees["b"]="香蕉";
    $trees[3]="樱桃";

if($txt){
    header('Content-Disposition: attachment; filename="'.$trees[$id].'.txt"');
    header('Content-type: text/'.($txt?'plain':'html').'; charset=utf-8');
    echo '您选择种了:'.$trees[$id].'树';
    die();
}else{
    echo '<h3>您选择种了:'.$trees[$id].'树';
?>

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