Detailed explanation of PHP database connection: from configuration to use

PHP is a high-level server-side programming language that is widely used to develop dynamic websites and web applications. In these applications, the database is an integral component. Database connection is the bridge for data interaction between PHP and the database. Mastering the configuration and use of database connection is one of the basic skills of PHP developers. This article will introduce in detail the configuration steps and usage of PHP database connection.

1. Configuration of database connection

In PHP, we can use a variety of different extensions to connect to the database, such as MySQLi, PDO, etc. In order to connect to the database, we first need to understand the basic configuration information of the database, including host name, user name, password, database name, etc. These configuration information need to be set according to the actual situation.

In the MySQL database, we can use the following code to create a database connection:

$servername = "localhost"; // 主机名
$username = "root"; // 用户名
$password = "password"; // 密码
$dbname = "mydatabase"; // 数据库名

$conn = new mysqli($servername, $username, $password, $dbname);

// 检查连接是否成功
if ($conn->connect_error) {
    die("连接失败: " . $conn->connect_error);
}

echo "连接成功";

In the above code, we first define the configuration information of the database, and then use new mysqli ()The function creates a database connection.

2. Use of database connection

Once the database connection is successfully established, we can use various SQL statements to operate the database. The following are some common database operation examples:

2.1 Query data

$sql = "SELECT * FROM users";
$result = $conn->query($sql);

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

In the above code, we use the SELECT * FROM users query statement to obtain the data of all users data, then iterate through the result set and output it.

2.2 Insert data

$sql = "INSERT INTO users (name, email) VALUES ('John Doe', 'john@example.com')";

if ($conn->query($sql) === TRUE) {
    echo "新记录插入成功";
} else {
    echo "Error: " . $sql . "<br>" . $conn->error;
}

In the above code, we use the INSERT INTO statement to insert a new user record into the database.

2.3 Update data

$sql = "UPDATE users SET name='Jane Doe' WHERE id=1";

if ($conn->query($sql) === TRUE) {
    echo "记录更新成功";
} else {
    echo "Error updating record: " . $conn->error;
}

In the above code, we use the UPDATE statement to update the name of the user record with id 1.

2.4 Delete data

$sql = "DELETE FROM users WHERE id=1";

if ($conn->query($sql) === TRUE) {
    echo "记录删除成功";
} else {
    echo "Error deleting record: " . $conn->error;
}

In the above code, we use the DELETE FROM statement to delete the user record with id 1.

3. Close the database connection

After we have finished using the database connection, we should close the connection in time to release resources. You can use the following code to close the database connection:

$conn->close();

4. Exception handling

During the process of database connection and operation, some exceptions may occur, such as database connection failure , SQL statement execution errors, etc. In order to catch and handle these exceptions, we can use try-catch statements for exception handling. The following is a simple example:

try {
    // 创建数据库连接
    $conn = new mysqli($servername, $username, $password, $dbname);

    // 设置异常模式为抛出异常
    $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

    // 执行数据库操作
    // ...

    // 关闭数据库连接
    $conn->close();
} catch(PDOException $e) {
    echo "数据库连接错误: " . $e->getMessage();
}

In the above code, we used the setAttribute() method to set the exception mode to throw an exception, and then used the try-catch statement to catch and Handle exceptions.

To sum up, this article introduces in detail the configuration steps and usage of PHP database connection. By mastering the configuration and use of database connections, you can develop PHP applications more efficiently and better operate and manage databases.

The above is the detailed content of Detailed explanation of PHP database connection: from configuration to use. For more information, please follow other related articles on the PHP Chinese website!