PHP 4.32上的xlsstream奇怪的输出

Question

我一直在尝试在此库中包含的样本excel中导出相同的数据：

Link to Library

并且我得到了一些像这样的奇怪输出：

OUTPUT

为什么，哦为什么......这里是我的代码：

<?php
include_once("header.auth.php");
    require_once "xlsstream/excel.php";
    $fecha_de_corrido=date("YmdHi");
    $export_file = "xlsfile://tmp/InformeCertificados_".$fecha_de_corrido.".xls"; 

$fp = fopen($export_file, "wb"); 
if (!is_resource($fp))
{ 
    die("Cannot open $export_file");
}

$assoc = array(
    array("Sales Person" => "Sam Jackson", "Q1" => "$3255", "Q2" => "$3167", "Q3" => 3245, "Q4" => 3943),
    array("Sales Person" => "Jim Brown", "Q1" => "$2580", "Q2" => "$2677", "Q3" => 3225, "Q4" => 3410),
    array("Sales Person" => "John Hancock", "Q1" => "$9367", "Q2" => "$9875", "Q3" => 9544, "Q4" => 10255),
);

fwrite($fp,serialize($assoc));

fclose($fp);


header ("Content-type: application/x-msexcel");
header ("Content-Disposition: attachment; filename=\"" . basename($export_file) . "\"" );
header ("Content-Description: PHP/INTERBASE Generated Data" );
        readfile($export_file);
        exit;
        ?>

Plz任何帮助都会很棒。