用php怎么从mysql拿数据库

<?php
// 连接MySQL数据库
$servername = "数据库服务器地址";
$username = "用户名";
$password = "密码";
$dbname = "数据库名";
$conn = new mysqli($servername, $username, $password, $dbname);

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

// 构建SQL查询语句
$sql = "SELECT * FROM 表名";

// 执行查询并获取结果集
$result = $conn->query($sql);

// 处理结果集
if ($result->num_rows > 0) {
    // 遍历每一行数据
    while ($row = $result->fetch_assoc()) {
        // 输出每行数据
        echo "ID: " . $row["id"] . "，姓名: " . $row["name"] . "，年龄: " . $row["age"];
        echo "<br>";
    }
} else {
    echo "没有结果";
}

// 关闭数据库连接
$conn->close();
?>

<?php
// 连接MySQL数据库
$servername = "数据库服务器地址";
$username = "用户名";
$password = "密码";
$dbname = "数据库名";
try {
    $conn = new PDO("mysql:host=$servername;dbname=$dbname", $username, $password);
    $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

    // 构建SQL查询语句
    $sql = "SELECT * FROM 表名";

    // 执行查询并获取结果集
    $stmt = $conn->prepare($sql);
    $stmt->execute();

    // 设置结果集返回的格式为关联数组
    $stmt->setFetchMode(PDO::FETCH_ASSOC);

    // 处理结果集
    while ($row = $stmt->fetch()) {
        // 输出每行数据
        echo "ID: " . $row["id"] . "，姓名: " . $row["name"] . "，年龄: " . $row["age"];
        echo "<br>";
    }
} catch (PDOException $e) {
    echo "连接失败: " . $e->getMessage();
}

// 关闭数据库连接
$conn = null;
?>