How to transfer database between different files in php

When developing a PHP website, database connection is an integral part. However, when we need to process multiple PHP files, how to pass database connections between different files? This is a common question and this article will show you how to pass a database between different PHP files.

1. Use global variables

In PHP, you can use global variables to transfer data between different files. Therefore, we can use global variables to pass the database connection. The following is an example:

In the db.php file, we establish a database connection and store it in a global variable $connection:

$server = 'localhost';
$username = 'root';
$password = '';
$database = 'test_db';

$connection = mysqli_connect($server, $username, $password, $database);

if (!$connection) {
    die("Connection failed: " . mysqli_connect_error());
}

In other PHPs that need to connect to the database In the file, we can use the global variable $connection to pass the connection:

require_once 'db.php';

$sql = "SELECT * FROM users";
$result = mysqli_query($connection, $sql);

if (mysqli_num_rows($result) > 0) {
    // 输出数据
    while($row = mysqli_fetch_assoc($result)) {
        echo "id: " . $row["id"]. " - Name: " . $row["name"]. "<br>";
    }
} else {
    echo "0 结果";
}

mysqli_close($connection);

As shown in the above code, in the file that needs to use the database connection, we import the db.php file through the require_once statement. We can then use the global variable $connection to execute the SQL query.

2. Store the connection in SESSION

In PHP, SESSION is used to store user information on the website. We can store the database connection in SESSION. In other PHP files that need to connect to the database, we can obtain the connection through SESSION. Here is an example:

In the db.php file, we establish a database connection and store it in SESSION:

$server = 'localhost';
$username = 'root';
$password = '';
$database = 'test_db';

$connection = mysqli_connect($server, $username, $password, $database);

if (!$connection) {
    die("Connection failed: " . mysqli_connect_error());
}

session_start();

$_SESSION['connection'] = $connection;

In other PHP files that need to connect to the database, we The connection can be obtained from SESSION:

session_start();

$connection = $_SESSION['connection'];

$sql = "SELECT * FROM users";
$result = mysqli_query($connection, $sql);

if (mysqli_num_rows($result) > 0) {
    // 输出数据
    while($row = mysqli_fetch_assoc($result)) {
        echo "id: " . $row["id"]. " - Name: " . $row["name"]. "<br>";
    }
} else {
    echo "0 结果";
}

mysqli_close($connection);

As shown in the above code, in the file that needs to use the database connection, we start SESSION through the session_start() function and obtain the connection from SESSION, and then we can use the connection to execute SQL queries.

Summary

In PHP, there are multiple ways to pass database connections between different files. Among them, the most common methods are to use global variables and SESSION. Using these techniques allows us to keep the code maintainable and scalable while writing large PHP projects. Hopefully this article will help you better understand database connections in PHP.

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