怎么用php连接数据库_PHP数据库连接配置与操作方法教程

配置PHP数据库连接需选择MySQLi或PDO方法，确保扩展启用；2. MySQLi支持过程和面向对象风格，通过mysqli_connect或new mysqli建立连接并检测错误；3. PDO提供跨数据库兼容性，使用DSN、用户名密码创建实例，并设置异常模式便于调试；4. 推荐用环境变量存储敏感信息，通过phpdotenv加载配置提升安全性；5. 连接后执行SELECT 1或查询数据库名等简单语句验证连通性，并测试增删改查操作。

If you are trying to connect to a database using PHP, proper configuration and setup are essential. Here are the steps to establish a successful connection:

The operating environment of this tutorial: MacBook Pro, macOS Sonoma

1. Using MySQLi (Procedural Style)

The MySQLi extension allows you to interact with MySQL databases in a procedural manner. This method is straightforward and widely supported.

• Ensure that the MySQLi extension is enabled in your php.ini file by checking for extension=mysqli.
• Use the mysqli_connect() function with parameters for server, username, password, and database name.
• Store the connection result in a variable and verify it using mysqli_connect_error() if the connection fails.
• Example code:

  $connection = mysqli_connect("localhost", "root", "password", "testdb");
  if (!$connection) {
      die("Connection failed: " . mysqli_connect_error());
  }
  

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2. Using MySQLi (Object-Oriented Style)

This approach uses the MySQLi class to create an instance of the connection, offering better code organization and reusability.

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• Create a new instance of mysqli by passing host, user, pass, and database arguments.
• Check for connection errors using the connect_error property.
• Example:

  $mysqli = new mysqli("localhost", "root", "password", "testdb");
  if ($mysqli->connect_error) {
      die("Connection failed: " . $mysqli->connect_error);
  }
  

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• After establishing the connection, you can execute queries using methods like query() or prepare().

3. Using PDO (PHP Data Objects)

PDO provides a consistent interface for accessing various databases, making your application more portable across different database systems.

• Ensure the PDO MySQL driver is enabled via extension=pdo_mysql in php.ini.
• Create a new PDO instance by specifying the DSN (Data Source Name), which includes the host and database name.
• Pass username and password as additional arguments.
• Set error mode to exception for easier debugging: $pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);.
• Example:

  try {
      $pdo = new PDO("mysql:host=localhost;dbname=testdb", "root", "password");
      $pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
  } catch (PDOException $e) {
      die("Connection failed: " . $e->getMessage());
  }
  

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4. Configuring Database Connection via Environment Variables

Storing credentials directly in code poses security risks. Using environment variables keeps sensitive data out of version control.

• Create a .env file in your project root and define keys like DB_HOST, DB_USER, DB_PASS, DB_NAME.
• Use a library like vlucas/phpdotenv to load these variables into $_ENV.
• Access them in your connection script:

  require_once 'vendor/autoload.php';
  $dotenv = Dotenv\Dotenv::createImmutable(__DIR__);
  $dotenv->load();
  $pdo = new PDO("mysql:host=" . $_ENV['DB_HOST'] . ";dbname=" . $_ENV['DB_NAME'], $_ENV['DB_USER'], $_ENV['DB_PASS']);
  

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• This method enhances security and simplifies configuration management across environments.

5. Testing the Connection and Performing Basic Queries

After connecting, validate functionality by executing a simple query to retrieve data or check server status.

• Run a basic SELECT query such as SELECT 1 to confirm connectivity.
• For MySQLi (procedural):

  $result = mysqli_query($connection, "SELECT 1");
  if ($result) echo "Database reachable.";
  

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• With PDO:

  $stmt = $pdo->query("SELECT DATABASE();");
  echo "Connected to: " . $stmt->fetchColumn();
  

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• You can also test INSERT, UPDATE, or CREATE operations after confirming the link works correctly.

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