如何在从php中插入数据后才显示表格

<?php
// 连接数据库
$servername = "数据库服务器地址";
$username = "数据库用户名";
$password = "数据库密码";
$dbname = "数据库名称";

$conn = new mysqli($servername, $username, $password, $dbname);
if ($conn->connect_error) {
    die("数据库连接失败: " . $conn->connect_error);
}

// 插入数据
$sql = "INSERT INTO 表名 (列1, 列2, 列3) VALUES ('值1', '值2', '值3')";
if ($conn->query($sql) === TRUE) {
    echo "数据插入成功";
} else {
    echo "数据插入失败: " . $conn->error;
}

// 查询数据
$sql = "SELECT * FROM 表名";
$result = $conn->query($sql);

// 显示表格
if ($result->num_rows > 0) {
    echo "<table>";
    echo "<tr><th>列1</th><th>列2</th><th>列3</th></tr>";
    while ($row = $result->fetch_assoc()) {
        echo "<tr><td>" . $row["列1"] . "</td><td>" . $row["列2"] . "</td><td>" . $row["列3"] . "</td></tr>";
    }
    echo "</table>";
} else {
    echo "没有数据";
}

$conn->close();
?>