How to use php to implement paging function (process analysis)

As the website develops and the page content becomes more and more, the practice of loading all the content at the beginning is gradually not accepted. As a result, pagination has gradually been widely adopted, providing a better user experience for websites that read large data sets. This article will introduce the process of implementing paging with PHP.

1. Preparation

Before starting to implement paging, you need to prepare some data. These data include the total amount of data and the amount of data to be displayed on each page. For example, we assume that we need to query user data in the database and set the amount of data to be displayed on each page to 10. In addition, the current page number also needs to be determined. This information will be passed to the paging script through URL parameters.

2. Database Query

First, a database query is required to obtain the total amount of data. For example, in this example, we want to query the total amount of data in the user table. The query statement is as follows:

SELECT COUNT(*) FROM users

By running this statement, we can know how many pieces of data there are in the user table. If the return value is 121, then we have 121 user data to process.

3. Calculate the number of pages

After getting the total amount of data, you need to calculate how many pages there are in total. This calculation method is very simple, just divide the total amount of data by the amount of data to be displayed on each page, and round up. In this example, 10 pieces of data are to be displayed on each page, and the total amount of data is 121 pieces, so a total of 12 pages are required.

4. Building paging links

Building paging links is the most critical step in the process of realizing the paging function. Page numbers and links need to be displayed on the page so that users can browse different pages easily. In this case, we need to build pagination links based on the current page count and the total page count.

We can use a for loop to traverse from 1 to the total number of pages to build a link for each page number, as shown below:

for($i=1;$i<=$total_pages;$i++){
    echo "<a href=&#39;pagination.php?page=".$i."&#39;>".$i."</a> ";
}

When building a link, the current page number should be used as a parameter passed to the link. In this example, the link address is pagination.php, the parameter is page, and the value is the number of each page. In this way, links to all page numbers can be constructed.

5. Paging data query

When the user clicks a link on a certain page, the paging script needs to query the database based on the page number and return the data of the current page. We need to use LIMIT and OFFSET to limit the number and starting position of query results.

For example, if the user clicks the link on page 3, the query statement should be as follows:

SELECT * FROM users LIMIT 10 OFFSET 20

This query statement will return 10 pieces of data starting from the 21st piece of data, that is Data on page 3. You can query the data of the current page by setting LIMIT and OFFSET to the amount of data to be displayed per page and the current page number -1 multiplied by the amount of data to be displayed per page.

6. Display paginated data

Finally, display paginated data on the page. In this example, we need to display user data from page 3. You can use a loop statement to traverse the data queried from the database and display the output on the page. The specific code is as follows:

$result = mysqli_query($conn, "SELECT * FROM users LIMIT 10 OFFSET 20");
while($row = mysqli_fetch_assoc($result)){
    echo $row['username']."<br />";
}

By running this code, 10 pieces of user data on page 3 will be displayed on the page.

The above is the main process of using PHP to implement paging. By querying the database, calculating the number of pages, building paging links, querying paging data based on page numbers, and finally displaying paging data on the page, users can easily browse large data sets.

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