Analysis of PHP paging principle Attachment: Simple example_PHP tutorial

1. Introduction

Paging display is a very common method of browsing and displaying large amounts of data, and 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 that the result set in the database is artificially divided 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 that fetches 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 value with the above set of sql statements to see if it is the same. thing. 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.

Copy to ClipboardQuoted content: [www.bkjia.com] //Establish a database connection
$link = mysql_connect("localhost", "mysql_user", "mysql_password")
or die("Could not connect: " . mysql_error());
//Get the current page number
if( isset($_GET['page']) ){
$page = intval( $_GET['page'] );
}
else{
$page = 1;
}
// Number of pages per page
$PageSize = 10;
// Get the total data volume
$sql = "select count(* ) as amount from table";
$result = mysql_query($sql);
$row = mysql_fetch_row($result);
$amount = $row['amount'];
// Calculate how many pages there are in total
if( $amount ){
if( $amount < $page_size ){ $page_count = 1; } //If the total data amount is less than $PageSize, then there is only one page
if( $amount % $page_size ){ //Get the remainder of the total data amount divided by the number of pages
$page_count = (int)($amount / $page_size) + 1; //If there is a remainder, the page The number is equal to the total data amount divided by the number of pages. The result is rounded and plus one
}else{
$page_count = $amount / $page_size; //If there is no remainder, the number of pages is equal to the total data amount divided by Results of the number of pages per page
}
}
else{
$page_count = 0;
}

// Page turning link
$page_string = '';
if( $page == 1 ){
$page_string .= 'First page|Previous page|';
}
else{
$page_string .= '|Previous page}
if( ($page == $page_count) || ($page_count == 0) ){
$page_string .= 'next page|last page';
}
else{
$page_string .= 'Next page|Last page';
}
// Get data and return the result in two-dimensional array format
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();
}
// There is no code to display the results, so that is beyond the scope of discussion. As long as you use foreach, you can easily use the obtained two-dimensional array to display the results
?>

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http://www.bkjia.com/PHPjc/364454.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/364454.htmlTechArticle1. Preface Pagination display is a very common method of browsing and displaying large amounts of data, which is the most common method in web programming. One of the commonly handled events. For web programming veterans, writing this code...