好奇怪啊，往记事本里添加数据，用\t分割，结果每个tab键的长度不一致？不一致？

源代码如下，是两个文件，一个提交数据，一个处理数据。<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" lang="zh-CN">
<head>
<title></title>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<meta name="description" content="" />
<style>
dl,dt,dd {margin: 0;}
</style>
</head>
    <body>
     <form action="processorder.php" method="post">
<div>
<dl>
<dt>Item</dt>
<dd>Quantity</dd>
<dt>Tires</dt>
<dd><input type="text" name="tireqty"/></dd>
<dt>oil</dt>
<dd><input type="text" name="oilqty"/></dd>
<dt>Spark plugs</dt>
<dd><input type="text" name="sparkqty"/></dd>
<dt>Shop Address</dt>
<dd><input type="text" name="address"/></dd>
<input type="submit" value="Submit Orders" />
</dl>
</div>
     </form>
    </body>
</html>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" lang="zh-CN">
<head>
<title>Order Results</title>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<meta name="description" content="" />
</head>
    <body>
     <h1>Bob's auto Parts</h1>
     <h2>Order Results</h2>
     <?php 
     echo "<p>Order Precessed at ";
     echo date('H:i,jS F');
     echo "</p>";
     ?><?php 
$totalqty = 0;
print_r($_POST);
echo "<br />";$tireqty = $_POST['tireqty'];
$oilqty  = $_POST['oilqty'];
$sparkqty= $_POST['sparkqty'];
$address = $_POST['address'];
$DOCUMENT_ROOT = $_SERVER['DOCUMENT_ROOT'];
$totalqty = $tireqty+$oilqty+$sparkqty;
$date = date('H:i,jS F Y');
echo "Item Ordered: $totalqty<br />";
if ($totalqty==0) {
    echo "You did not order anything on the Bob's site!";
} else {
    if ($tireqty>0) {
        echo $tireqty."tireqty<br />";
    } 
    if ($oilqty>0){
        echo $oilqty."oilqty<br />";
    }
    if ($sparkqty>0) {
        echo $sparkqty."sparkqty<br />";
    }
}$totalamount = 0.00;define('TIREPRICE', 100);
define('OLIPRICE', 10);
define('SPARKPRICE', 4);
$totalamount =  $tireqty*TIREPRICE
+$oilqty*OLIPRICE
+$sparkqty*SPARKPRICE;
$totalamount = number_format($totalamount,2,'.','');
echo "<p>Totalamount is $".$totalamount."</p>";
$tax_rate = 0.1;
$totalamount = $totalamount*(1+$tax_rate);
echo "Total including tax:$".$totalamount."<br />";$putstrings =$date."\t".$tireqty." tires\t".$oilqty." oil\t".$sparkqty." spark plugs\t"."Totalamount $".$totalamount."\t"."Address ".$address."\r\n";
print_r($DOCUMENT_ROOT);
@$fp = fopen("$DOCUMENT_ROOT/../orders/order.txt", 'ab');
flock($fp, LOCK_EX);
if (!$fp) {
    echo "<p>your order is not processed at this time.
    Please try again later.</p></body></html>";
    exit;
}
fwrite($fp, $putstrings,strlen($putstrings));
flock($fp, LOCK_UN);
fclose($fp);
echo "Order Written!";?>
</body>
</html>