PHP paging Detailed explanation of PHP paging display production

1. Introduction

Paging display is a very common method of browsing and displaying large amounts of data, and it is one of the most commonly processed events in web programming. For veterans of web programming, writing this kind of code is as natural as breathing, but for beginners, they are often confused about this issue, so I specially wrote this article to explain this issue in detail, and strive to let readers Friends who have finished this article will have some understanding of the principles and implementation methods of paging display. This article is suitable for beginners to read, and all sample codes are written in PHP.

2. Principle

The so-called paging display means artificially dividing the result set in the database into sections for display. Two initial parameters are required here:

How many records per page ($PageSize)?

What page is the current page ($CurrentPageID)?

Now as long as you give me another result set, I can display a specific result.

As for other parameters, such as: previous page ($PreviousPageID), next page ($NextPageID), total number of pages ($numPages), etc., they can all be obtained based on the previous things.

Take the mysql database as an example. If you want to intercept a certain piece of content from the table, the sql statement can be used: select * from table limit offset, rows. Take a look at the following set of SQL statements and try to find the rules.

The first 10 records: select * from table limit 0,10

The 11th to 20th records: select * from table limit 10,10

The 21st to 30th records: select * from table limit 20,10

...

This set of sql statements is actually the sql statement for fetching data from each page of the table when $PageSize=10. We can summarize such a template:

select * from table limit ($CurrentPageID - 1 ) * $PageSize, $PageSize

Take this template and substitute the corresponding values ​​​​and compare it with the above set of sql statements to see if that is the case. After solving the most important problem of how to obtain the data, all that is left is to pass the parameters, construct the appropriate SQL statement and then use PHP to obtain the data from the database and display it. Below I will explain it with specific code.

3. Simple code

Please read the following code in detail, debug and run it yourself. It is best to modify it once and add your own functions, such as search, etc.

<?php 
// 建立数据库连接 
$link = mysql_connect("localhost", "mysql_user", "mysql_password") 
or die("Could not connect: " . mysql_error()); 
// 获取当前页数 
if( isset($_GET[&#39;page&#39;]) ){ 
$page = intval( $_GET[&#39;page&#39;] ); 
} 
else{ 
$page = 1; 
} 
// 每页数量 
$PageSize = 10; 
// 获取总数据量 
$sql = "select count(*) as amount from table"; 
$result = mysql_query($sql); 
$row = mysql_fetch_row($result); 
$amount = $row[&#39;amount&#39;]; 
// 记算总共有多少页 
if( $amount ){ 
if( $amount < $page_size ){ $page_count = 1; } //如果总数据量小于$PageSize，那么只有一页 
if( $amount % $page_size ){ //取总数据量除以每页数的余数 
$page_count = (int)($amount / $page_size) + 1; //如果有余数，则页数等于总数据量除以每页数的结果取整再加一 
}else{ 
$page_count = $amount / $page_size; //如果没有余数，则页数等于总数据量除以每页数的结果 
} 
} 
else{ 
$page_count = 0; 
} 
// 翻页链接 
$page_string = &#39;&#39;; 
if( $page == 1 ){ 
$page_string .= &#39;第一页|上一页|&#39;; 
} 
else{ 
$page_string .= &#39;<a href=?page=1>第一页</a>|<a href=?page=&#39;.($page-1).&#39;>上一页</a>|&#39;; 
} 
if( ($page == $page_count) || ($page_count == 0) ){ 
$page_string .= &#39;下一页|尾页&#39;; 
} 
else{ 
$page_string .= &#39;<a href=?page=&#39;.($page+1).&#39;>下一页</a>|<a href=?page=&#39;.$page_count.&#39;>尾页</a>&#39;; 
} 
// 获取数据，以二维数组格式返回结果 
if( $amount ){ 
$sql = "select * from table order by id desc limit ". ($page-1)*$page_size .", $page_size"; 
$result = mysql_query($sql); 
while ( $row = mysql_fetch_row($result) ){ 
$rowset[] = $row; 
} 
}else{ 
$rowset = array(); 
} 
// 没有包含显示结果的代码，那不在讨论范围，只要用foreach就可以很简单的用得到的二维数组来显示结果 
?>

4. OO style code

The database connection in the following code is processed using the pear db class

<?php 
// FileName: Pager.class.php 
// 分页类，这个类仅仅用于处理数据结构，不负责处理显示的工作 
Class Pager 
{ 
var $PageSize; //每页的数量 
var $CurrentPageID; //当前的页数 
var $NextPageID; //下一页 
var $PreviousPageID; //上一页 
var $numPages; //总页数 
var $numItems; //总记录数 
var $isFirstPage; //是否第一页 
var $isLastPage; //是否最后一页 
var $sql; //sql查询语句 
function Pager($option) 
{ 
global $db; 
$this->_setOptions($option); 
// 总条数 
if ( !isset($this->numItems) ) 
{ 
$res = $db->query($this->sql); 
$this->numItems = $res->numRows(); 
} 
// 总页数 
if ( $this->numItems > 0 ) 
{ 
if ( $this->numItems < $this->PageSize ){ $this->numPages = 1; } 
if ( $this->numItems % $this->PageSize ) 
{ 
$this->numPages= (int)($this->numItems / $this->PageSize) + 1; 
} 
else 
{ 
$this->numPages = $this->numItems / $this->PageSize; 
} 
} 
else 
{ 
$this->numPages = 0; 
} 
switch ( $this->CurrentPageID ) 
{ 
case $this->numPages == 1: 
$this->isFirstPage = true; 
$this->isLastPage = true; 
break; 
case 1: 
$this->isFirstPage = true; 
$this->isLastPage = false; 
break; 
case $this->numPages: 
$this->isFirstPage = false; 
$this->isLastPage = true; 
break; 
default: 
$this->isFirstPage = false; 
$this->isLastPage = false; 
} 
if ( $this->numPages > 1 ) 
{ 
if ( !$this->isLastPage ) { $this->NextPageID = $this->CurrentPageID + 1; } 
if ( !$this->isFirstPage ) { $this->PreviousPageID = $this->CurrentPageID - 1; } 
} 
return true; 
} 
/*** 
* 
* 返回结果集的数据库连接 
* 在结果集比较大的时候可以直接使用这个方法获得数据库连接，然后在类之外遍历，这样开销较小 
* 如果结果集不是很大，可以直接使用getPageData的方式获取二维数组格式的结果 
* getPageData方法也是调用本方法来获取结果的 
* 
***/ 
function getDataLink() 
{ 
if ( $this->numItems ) 
{ 
global $db; 
$PageID = $this->CurrentPageID; 
$from = ($PageID - 1)*$this->PageSize; 
$count = $this->PageSize; 
$link = $db->limitQuery($this->sql, $from, $count); //使用Pear DB::limitQuery方法保证数据库兼容性 
return $link; 
} 
else 
{ 
return false; 
} 
} 
/*** 
* 
* 以二维数组的格式返回结果集 
* 
***/ 
function getPageData() 
{ 
if ( $this->numItems ) 
{ 
if ( $res = $this->getDataLink() ) 
{ 
if ( $res->numRows() ) 
{ 
while ( $row = $res->fetchRow() ) 
{ 
$result[] = $row; 
} 
} 
else 
{ 
$result = array(); 
} 
return $result; 
} 
else 
{ 
return false; 
} 
} 
else 
{ 
return false; 
} 
} 
function _setOptions($option) 
{ 
$allow_options = array( 
&#39;PageSize&#39;, 
&#39;CurrentPageID&#39;, 
&#39;sql&#39;, 
&#39;numItems&#39; 
); 
foreach ( $option as $key => $value ) 
{ 
if ( in_array($key, $allow_options) && ($value != null) ) 
{ 
$this->$key = $value; 
} 
} 
return true; 
} 
} 
?> 
<?php 
// FileName: test_pager.php 
// 这是一段简单的示例代码，前边省略了使用pear db类建立数据库连接的代码 
require "Pager.class.php"; 
if ( isset($_GET[&#39;page&#39;]) ) 
{ 
$page = (int)$_GET[&#39;page&#39;]; 
} 
else 
{ 
$page = 1; 
} 
$sql = "select * from table order by id"; 
$pager_option = array( 
"sql" => $sql, 
"PageSize" => 10, 
"CurrentPageID" => $page 
); 
if ( isset($_GET[&#39;numItems&#39;]) ) 
{ 
$pager_option[&#39;numItems&#39;] = (int)$_GET[&#39;numItems&#39;]; 
} 
$pager = @new Pager($pager_option); 
$data = $pager->getPageData(); 
if ( $pager->isFirstPage ) 
{ 
$turnover = "首页|上一页|"; 
} 
else 
{ 
$turnover = "<a href=&#39;?page=1&numItems=".$pager->numItems."&#39;>首页</a>|<a href=&#39;?page=".$pager->PreviousPageID."&numItems=".$pager->numItems."&#39;>上一页</a>|"; 
} 
if ( $pager->isLastPage ) 
{ 
$turnover .= "下一页|尾页"; 
} 
else 
{ 
$turnover .= "<a href=&#39;?page=".$pager->NextPageID."&numItems=".$pager->numItems."&#39;>下一页</a>|<a href=&#39;?page=".$pager->numPages."&numItems=".$pager->numItems."&#39;>尾页</a>"; 
} 
?>

There are two things that need to be explained:

This class only processes data and is not responsible for processing display , because I think it is a bit reluctant to put both data processing and result display into one class. When displaying, the situation and requirements are changeable. It is better to handle it according to the results given by the class. A better way is to inherit a subclass of your own based on the Pager class to display different paginations. For example, displaying the user pagination list can be:

<?php 
Class MemberPager extends Pager 
{ 
function showMemberList() 
{ 
global $db; 
$data = $this->getPageData(); 
// 显示结果的代码 
// ...... 
} 
} 
/// 调用 
if ( isset($_GET[&#39;page&#39;]) ) 
{ 
$page = (int)$_GET[&#39;page&#39;]; 
} 
else 
{ 
$page = 1; 
} 
$sql = "select * from members order by id"; 
$pager_option = array( 
"sql" => $sql, 
"PageSize" => 10, 
"CurrentPageID" => $page 
); 
if ( isset($_GET[&#39;numItems&#39;]) ) 
{ 
$pager_option[&#39;numItems&#39;] = (int)$_GET[&#39;numItems&#39;]; 
} 
$pager = @new MemberPager($pager_option); 
$pager->showMemberList(); 
?>

The second thing that needs to be explained is the compatibility of different databases. The way to intercept a result in different databases is different.

mysql: select * from table limit offset, rows

pgsql: select * from table limit m offset n

......

So when you want to get the results in the class, you need to use the limitQuery of the pear db class method.

ok, I’ll take credit when I’m done. I hope you don’t feel it’s a waste of time if you take the time to read these words.

The above introduces PHP paging and a detailed explanation of PHP paging display production, including PHP paging content. I hope it will be helpful to friends who are interested in PHP tutorials.

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php paging class code

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