How to use database query and result paging functions for data paging and display in PHP?

How to use database query and result paging functions for data paging and display in PHP?

When developing web applications, it is often necessary to process a large amount of data and display it on the page, such as product lists, news lists, etc. When the amount of data is large, loading all the data onto the page at once not only affects performance, but may also cause the page to load slowly. At this time, paging the data is a common and effective way to deal with it.

This article will introduce how to use the database query and result paging functions in PHP for data paging and display. We will use MySQL as a database example and explain in detail with code examples.

Step 1: Connect to the database

First, we need to use PHP's MySQLi extension or the PDO library to connect to the MySQL database. The following is a sample code to connect to the database:

<?php
$servername = "localhost";
$username = "your_username";
$password = "your_password";
$dbname = "your_database";

// 使用MySQLi连接数据库
$conn = new mysqli($servername, $username, $password, $dbname);
if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
}

// 使用PDO连接数据库
try {
    $conn = new PDO("mysql:host=$servername;dbname=$dbname", $username, $password);
    $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    echo "Connected successfully";
} catch(PDOException $e) {
    echo "Connection failed: " . $e->getMessage();
}
?>

In the above code, you need to replace your_username, your_password and your_database with the actual Database user name, password and database name.

Step 2: Execute the query and paginate

Next, we will execute the query and use the pagination function to paginate the results. The following is an example paging function code:

<?php
function getProducts($conn, $limit, $offset) {
    $sql = "SELECT * FROM products LIMIT $limit OFFSET $offset";
    $stmt = $conn->prepare($sql);
    $stmt->execute();

    $result = $stmt->fetchAll(PDO::FETCH_ASSOC);
    return $result;
}

$limit = 10; // 每页显示的数据数量
$page = isset($_GET['page']) ? $_GET['page'] : 1; // 当前页码
$offset = ($page - 1) * $limit; // 计算偏移量

$products = getProducts($conn, $limit, $offset);
$totalRows = $conn->query("SELECT COUNT(*) FROM products")->fetchColumn();
$totalPages = ceil($totalRows / $limit);
?>

In the above code, the getProducts function accepts the connection object, the amount of data displayed per page $limit and the offset The amount $offset is used as a parameter to execute the query and return the query results. $limit and $offset are obtained by calculating the current page number $page.

$totalRowsThe variable is used to save the total number of data rows, which is obtained by executing the SELECT COUNT(*) query. $totalPagesThe variable is used to hold the total number of pages, calculated by dividing the total number of rows of data by the amount of data displayed on each page.

Step 3: Display the paginated results

Finally, we will use HTML and PHP to display the paginated results. Here is a simple sample code:

<?php
foreach ($products as $product) {
    echo "<h3 id="product-name">{$product['name']}</h3>";
    echo "<p>{$product['description']}</p>";
    echo "<hr>";
}

// 分页链接
for ($i = 1; $i <= $totalPages; $i++) {
    echo "<a href='?page=$i'>$i</a> ";
}
?>

In the above code, we use a loop to iterate through the query results and display the name and description of each product on the page. Pagination links are generated cyclically based on the total number of pages, and each link corresponds to a different page number.

Through the above three steps, we can use database query and result paging functions to easily paginate and display data in PHP. This improves page loading performance and improves user experience. Of course, in actual development, you may need to add some additional functions, such as search, sorting, etc., to meet more needs.

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