如何在php里查询表格

<code class="php">$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "database";

// 创建连接
$conn = new mysqli($servername, $username, $password, $dbname);

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

<code class="php">$sql = "SELECT * FROM table_name";</code>

<code class="php">$result = $conn->query($sql);

// 检查是否执行成功
if (!$result) {
    die("查询失败: " . $conn->error);
}</code>

<code class="php">// 逐行返回结果
while ($row = $result->fetch_assoc()) {
    // 访问列数据
    echo $row["column_name"] . "\n";
}

// 释放结果集
$result->free();</code>

<code class="php">$conn->close();</code>

<code class="php">// 建立连接
$conn = new mysqli("localhost", "username", "password", "database");

// 执行查询
$result = $conn->query("SELECT * FROM users");

// 遍历结果
while ($row = $result->fetch_assoc()) {
    echo "姓名：{$row["name"]}, 年龄：{$row["age"]}\n";
}

// 关闭连接
$conn->close();</code>