PHP 代码显示偏移误差

我是聪明的php模板系统的初学者，我正在读一本书Smarty PHP Template Programming。第2章的第一个例子如下。

在根文件夹中，我们有一个名为 data.txt 的文件，其中包含以下信息。

Title=> Building Websites with VB.NET and DotNetNuke 3.0 
Image=> 1904811272.jpg 
Author=> Daniel N. Egan 
Description=> A practical guide to creating and maintaining your own website with DotNetNuke, the free, open source evolution of Microsoft's IBuySpy Portal 
Year=> 2005 
Price=> 39.99 
Title=> SSL VPN : Understanding, evaluating and planning secure, web-based remote access 
Image=> 1904811078.jpg 
Author=> Joseph Steinberg, Tim Speed, Simon Jenner 
Description=> A comprehensive overview of SSL VPN technologies and design strategies 
Year=> 2005 
Price=> 49.99 
Title=> Windows Server 2003 Active Directory Design and Implementation=> Creating, Migrating, and Merging Networks 
Image=> 1904811086.jpg 
Author=> John Savill 
Description=> A unique, scenario-based approach to selecting and implementing the best Active Directory design for your environment 
Year=> 2005 
Price=> 59.99

下一步是从data.txt检索数据。为此，根文件夹中有一个名为 get_data.php 的文件，其中包含以下内容：

<?php
    class books {
        public $title = array(); 
        public $image = array(); 
        public $author = array(); 
        public $description = array(); 
        public $year = array();
        public $price = array(); 
        private $filename = "data.txt";
        //class constructor
        function __construct()
            {
                //get the lines as an array
                $i=-1;
                $lines = file($this->filename);
                // strip "'n" at the end of each array
                // get each variable in an array
                foreach ( $lines as $line) {
                if (strlen($line) > 2) {
                    $line = rtrim($line);
                    list($what, $content) = explode("=>", $line);
                    if ($what == "Title") {
                        $i++;
                        $this->title[$i]=$content;
                        }
                    elseif ($what == "Image") {
                        $this->image[$i]=$content;
                        }
                    elseif ($what == "Author") {
                        $this->author[$i]=$content;
                        }
                    elseif ($what == "Description") {
                        $this->description[$i]=$content;
                        }
                    elseif ($what == "Year") {
                        $this->year[$i]=$content;
                        }
                    elseif ($what == "Price") {
                        $this->price[$i]=$content;
                        };
                        };
                    };
                } // end constructor
                } // end GetData

逻辑层负责从业务角度进行数据验证。在此示例中，我们将对 2005 年出版的图书应用百分之十的折扣，对 2004 年出版的图书应用百分之二十的折扣。我们需要在根文件夹中创建一个名为 books 的文件.php如图所示

<?php
class bo_books {
//public
public $title = array();
public $image = array();
public $author = array();
public $description = array();
public $year = array();
public $price = array();
public $discount = array();
public $discounted = array();
//private
protected $DataObject;
function __construct()
{
$this->DataObject = new books();
}
public function apply_discount()
{
$this->title = $this->DataObject->title;
$this->image = $this->DataObject->image;
$this->author = $this->DataObject->author;
$this->description = $this->DataObject->description;
$this->year = $this->DataObject->year;
$this->price = $this->DataObject->price;
$j = 0;
foreach($this->year as $year)
{
if ($this->year[$j] == '2004')
$this->discount[$j] = '20';
elseif ($this->year[$j] == '2005')
$this->discount[$j] = '10';
$this->discounted[$j] = intval($this->price[$j] * (100 - $this->discount[$j]) ) / 100 ;
$j++;
};
} // end function apply_discount()
} // end class bo_books

：首先，我们需要将变量从业务逻辑层传递到表示层。在根文件夹中，我们创建一个名为 index 的文件.php如下所示：

<?php
require("libs/Smarty.class.php");
require_once("get_data.php");
require_once("books.php");
$book = new bo_books();
$book->apply_discount();
$smarty = new Smarty; 
$smarty->assign("book",$book);
$smarty->display('index.tpl');
?>

接下来，我们在templates文件夹中创建一个index.tpl文件

<html>
<head> <title> Site Architecture Example </title>
</head>
<body>
<table border="0" width="100%">
<tr>
<td align="left">
<a href="http://www.packtpub.com">
<img src="images'Packt.png" border="0">
</a>
<img src="images'focused.gif">
</td>
<td>
<h1> Chapter 2 Example </h1>
</td>
</tr>
</table>
<br>
Here are the books in a two-column table :
<br> <br>
<table border="1" width="100%">
{section name=tbl loop=$book->title}
{if %tbl.index% is not odd}
<tr>
{/if}
<td align="left">
<table>
<tr>
<td>
<img src="images'{$book->image[tbl]}" width="220">
</td>
<td valign="top">
<font size=+1><b> {$book->title[tbl]} </b></font><br>
<font size=-1 color=blue><b> {$book->author[tbl]} </b></font><br>
{$book->description[tbl]} <br>
Year: {$book->year[tbl]} <br>
<font size=-1>Cover Price: <s>${$book->price[tbl]}</s></font> <br>
Our Price: ${$book->discounted[tbl]}
<font color=red> save {$book->discount[tbl]} % </font>
</td>
</tr>
</table>
</td>
{if %tbl.index% is odd}
</tr>
{/if}
{/section}
</table>
</body>
</html>

当我运行程序时

注意：未定义的偏移量：第 28 行的 C：''wamp''www''MyCode''get_data.php 中的 1 被打开。

get_data.php上的第 28 行是

list($what, $content) = explode("=>", $line);

任何人都可以提出一些建议甚至帮助吗？