在php中怎么连接mysql

<?php
// 数据库配置
$host = 'localhost';
$username = 'your_username';
$password = 'your_password';
$database = 'your_database';

// 创建连接
$conn = new mysqli($host, $username, $password, $database);

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

// 执行查询
$sql = "SELECT id, name FROM your_table";
$result = $conn->query($sql);

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

// 关闭连接
$conn->close();
?>

<?php
// 数据库配置
$host = 'localhost';
$username = 'your_username';
$password = 'your_password';
$database = 'your_database';

try {
    // 创建PDO实例
    $conn = new PDO("mysql:host=$host;dbname=$database", $username, $password);
    // 设置PDO错误模式为异常
    $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

    // 执行查询
    $stmt = $conn->prepare("SELECT id, name FROM your_table");
    $stmt->execute();

    // 设置结果集为关联数组
    $result = $stmt->setFetchMode(PDO::FETCH_ASSOC);
    foreach($stmt->fetchAll() as $row) {
        echo "id: " . $row["id"]. " - Name: " . $row["name"]. "<br>";
    }
} catch(PDOException $e) {
    echo "连接失败: " . $e->getMessage();
}

// 关闭连接
$conn = null;
?>