The most common method of connecting to a MySQL database is to use PHP's mysqli or PDO extension. 1. Use mysqli: Create connection functions through object-oriented mode, set the host, username, password and database name, terminate the script when the connection fails and output error information; pay attention to enabling mysqli extension, avoid directly exposing errors, and manage configuration information independently. 2. Use PDO: Create a PDO instance and set connection parameters and error handling mode to catch exceptions to handle connection errors; its advantages include supporting preprocessing statements, better error handling and object-oriented development. Common problems include username or password errors, database service not started, host address errors, or firewall restrict access to ports; it is recommended to encapsulate the connection function into independent files and manage them in a unified manner, and the production environment records errors to the log instead of directly displaying them.

The most common method to connect to a MySQL database is to use the mysqli or PDO extension provided by PHP. Below I will give a simple but practical connection function, which is suitable for project requirements in different scenarios.

Connect to the database using mysqli

mysqli is an extension in PHP that is specifically used to operate MySQL, supporting object-oriented and procedural writing. Here is a connection function that uses object-oriented method:

 function connectDB() {
    $host = 'localhost';
    $username = 'your_username';
    $password = 'your_password';
    $database = 'your_database';

    $conn = new mysqli($host, $username, $password, $database);

    if ($conn->connect_error) {
        die("Connection failed: " . $conn->connect_error);
    }

    return $conn;
}

How to use:

 $conn = connectDB();
// Next, you can perform query and other operations

Note:

• Make sure mysqli extension is enabled on the server
• If the connection fails, it is recommended not to directly output error messages to prevent the exposure of sensitive information
• Database configuration information can be placed in a separate configuration file for convenient unified management

Connecting to a database using PDO

PDO is a more general database abstraction layer that supports multiple database types. If you consider possible switching database types in the future, it is recommended to use PDO.

 function connectDB() {
    $host = 'localhost';
    $dbname = 'your_database';
    $username = 'your_username';
    $password = 'your_password';

    try {
        $conn = new PDO("mysql:host=$host;dbname=$dbname;charset=utf8mb4", $username, $password);
        $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
        return $conn;
    } catch (PDOException $e) {
        die("Connection failed: " . $e->getMessage());
    }
}

advantage:

• Supports preprocessing statements to prevent SQL injection
• Better error handling mechanism
• More suitable for object-oriented development

FAQs and Suggestions

• Common reasons why you can't connect to a database:

  • Incorrect database username or password
  • Database service not started
  • The database host address is incorrect (for example, the remote database should be filled in the IP address)
  • Firewall restricts access to database ports (usually 3306)

• It is recommended to encapsulate the connection function into a class or a separate file: this way, the database connection can be managed uniformly and avoid duplicate code. For example, you can create a Database.php file that is specifically designed to handle connections and closures.

• Do not display original error messages in the production environment: record the error messages into a log file, rather than output them directly to the page to prevent them from exploiting them.

Basically that's it. Connecting to the database is the basic step of development. Although it is not complicated, handling the details well can avoid many subsequent problems.

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