php如何使用MySQL数据库？

<?php
// 数据库连接参数
$host = 'localhost';
$user = 'root';
$password = '123456';
$database = 'test';

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

// 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";
?>

$sql = "SELECT * FROM users";  // 查询users表中的所有数据
$result = $conn->query($sql);

if ($result->num_rows > 0) {
    while($row = $result->fetch_assoc()) {
        echo "id: " . $row["id"]. " - 姓名: " . $row["name"]. " - 年龄: " . $row["age"]. "<br>";
    }
} else {
    echo "没有数据";
}

$sql = "INSERT INTO users (name, age) VALUES ('Tom', 25)";
if ($conn->query($sql) === TRUE) {
    echo "插入数据成功";
} else {
    echo "插入数据失败: " . $conn->error;
}

$sql = "UPDATE users SET age = 26 WHERE id = 1";
if ($conn->query($sql) === TRUE) {
    echo "更新数据成功";
} else {
    echo "更新数据失败: " . $conn->error;
}

$sql = "DELETE FROM users WHERE id = 1";
if ($conn->query($sql) === TRUE) {
    echo "删除数据成功";
} else {
    echo "删除数据失败: " . $conn->error;
}

// 关闭连接
$conn->close();