PHP development article publishing system paging program

Paging program

The main principles of paging are shown in the figure below:

Note: Define the number of data items to be displayed on each page in advance (assuming three pieces of data on one page), and calculate the total number of pages based on the total number of data items in the database.

The output page uses the limit keyword of the database query statement. The first page is the 3 pieces of data starting from the 0th piece of data, the second page is the 3 pieces of data starting from the 3rd piece of data, and the nth page is the 3 pieces of data starting from the (n- 1) *3 pieces of data starting from 3 pieces of data

Now that the principle has been explained, let’s take a look at the actual program. The comments in the program are very clear. You can observe and understand line by line

<?php
//分页功能
//连接数据库
require_once("connect.php");
$page = isset($_GET['page'])?intval($_GET['page']):1;//设置当前页数，没有则设置为1
$num=3;//每页显示3条数据
/*
首先我们要获取数据库中到底有多少数据，才能判断具体要分多少页，总页数 具体的公式就是
总数据数 除以 每页显示的条数，有余进一 。
也就是说10/3=3.3333=4 有余数就要进一。
*/
$sql="select * from article";
$result=mysqli_query($conn,$sql);
$total=mysqli_num_rows($result);//查询数据的总条数
$pagenum=ceil($total/$num);//获得总页数
//假如传入的页数参数page 大于总页数 pagenum，则显示错误信息
if($page>$pagenum || $page == 0){
       echo "<script>alert('没有内容了');history.go(-1);</script>";
       exit;
}
 $offset=($page-1)*$num;        
/* 获取limit的第一个参数的值 offset ，假如第一页则为(1-1)*10=0,第二页为(2-1)*10=10。             (传入的页数-1) * 每页的数据 得到limit第一个参数的值*/
$sql="select * from article limit $offset,$num ";
$info=mysqli_query($conn,$sql);   //获取相应页数所需要显示的数据
//获取最新添加的前六条数据
$sql_new="select  id,title from article order by dateline desc limit 0,6 ";
$info_title=mysqli_query($conn,$sql_new);
?>