使用MySQLi过程化风格通过mysqli_connect()连接数据库，并用mysqli_close()关闭连接。2. MySQLi对象化风格以面向对象方式创建连接，使用$connection->query()执行查询并用$connection->close()关闭连接。3. PDO提供跨数据库一致性，通过new PDO()实例化并设置PDO::ATTR_ERRMODE异常模式增强错误处理。4. 通过PDO的SSL选项或MySQLi的mysqli_ssl_set()启用SSL加密连接以提升安全性。5. PDO中设置PDO::ATTR_PERSISTENT=true可实现持久连接，但需注意连接复用带来的资源管理问题。
If you are trying to connect PHP to a database, it's essential to use proper connection methods. Here are several ways to establish and manage database connections in PHP:
The operating environment of this tutorial: MacBook Pro, macOS Sonoma
1. Using MySQLi (Procedural Style)
MySQLi supports both procedural and object-oriented programming approaches. The procedural style uses functions to interact with the MySQL database.
- Use mysqli_connect() to initiate a connection by providing hostname, username, password, and database name.
- Check if the connection was successful using mysqli_connect_error() to handle failures gracefully.
- After connecting, execute queries using mysqli_query() for operations like SELECT, INSERT, or UPDATE.
- Always close the connection at the end using mysqli_close() to free up resources.
2. Using MySQLi (Object-Oriented Style)
This approach treats the database connection as an object, promoting cleaner and more maintainable code structure.
立即学习“PHP免费学习笔记（深入）”；
PHP5学习对象教程由美国人古曼兹、贝肯、瑞桑斯编著，简张桂翻译，电子工业出版社于2007年12月1日出版的关于PHP5应用程序的技术类图书。该书全面介绍了PHP 5中的新功能、编程方法及设计模式，还分析阐述了PHP 5中新的数据库连接处理、错误处理和XML处理等机制，帮助读者系统了解、熟练掌握和高效应用PHP。
- Create a new mysqli object by passing host, user, password, and database parameters to its constructor.
- Use the object’s methods such as $connection->query() to run SQL statements.
- Handle errors using $connection->connect_error instead of global functions.
- Close the connection explicitly with $connection->close().
3. Using PDO (PHP Data Objects)
PDO provides a consistent interface for accessing various databases, not just MySQL, making your application more portable.
- Instantiate a new PDO object with a DSN string containing driver type, host, port, and database name.
- Pass username and password as additional arguments to enable authentication.
- Set attributes like PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION to throw exceptions on errors.
- Execute prepared statements using prepare() and execute() methods to prevent SQL injection.
4. Establishing Secure Connections with SSL
To enhance security when connecting to remote databases, enforce encrypted communication using SSL/TLS.
- In PDO, add SSL options in the driver options array such as PDO::MYSQL_ATTR_SSL_CA to specify certificate authorities.
- For MySQLi, use mysqli_ssl_set() before connecting, providing paths to key, certificate, and CA files.
- Verify that the server requires SSL by checking the connection status through SHOW STATUS LIKE 'Ssl_cipher'.
5. Handling Persistent Connections
Persistent connections can improve performance by reusing existing database connections across requests.
- In PDO, enable persistence by setting PDO::ATTR_PERSISTENT => true in the options array during instantiation.
- Be cautious with persistent connections in high-traffic applications to avoid exhausting database connection limits.
- Ensure proper cleanup of transactions and prepared statements to prevent interference between requests.
