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Tips and methods for using HTML to read databases

PHPz

Apr 09, 2024 pm 01:45 PM

mysqlhtmlTips and Methods

为了使用 HTML 从数据库读取数据，有几种方法：使用 AJAX 调用，通过异步通信以无缝方式检索数据；使用 WebSockets，建立持久连接以实现实时数据传输；并且将响应格式化为 JSON，以便轻松客户端解析和处理。

Tips and methods for using HTML to read databases

利用 HTML 读取数据库：技巧与方法

简介

在 Web 应用程序中，从数据库读取数据是至关重要的任务。利用 HTML 作为客户端语言，我们可以轻松地与数据库交互并动态显示数据。本文介绍了几种有效的技巧和方法，帮助你有效地使用 HTML 读取数据库。

AJAX 调用

AJAX (Asynchronous JavaScript and XML) 允许你在不重新加载整个页面的情况下，与服务器进行异步通信。这使得从数据库读取数据变得高效且无缝。以下是使用 AJAX 调用读取数据的代码示例：

function getCustomers() {
  var xhr = new XMLHttpRequest();
  xhr.open("GET", "get_customers.php");
  xhr.onload = function() {
    if (xhr.status === 200) {
      var customers = JSON.parse(xhr.responseText);
      displayCustomers(customers);
    } else {
      alert("Error fetching customers.");
    }
  };
  xhr.send();
}

此函数通过 AJAX 调用向 get_customers.php 文件发送请求，后者从数据库检索客户数据。响应作为 JSON 格式返回，并在客户端解析和显示。

Web Sockets

Web Sockets 是另一种实现实时通信的强大技术。它允许客户端与服务器建立持久连接，从而可以持续读取数据库数据。以下是用 WebSocket 读取数据库数据的示例代码：

var websocket = new WebSocket("ws://localhost:8080");
websocket.onopen = function() {
  websocket.send("get_customers");
};
websocket.onmessage = function(event) {
  var data = JSON.parse(event.data);
  if (data.type == "customers") {
    displayCustomers(data.customers);
  }
};

此代码使用 WebSocket 对象连接到服务器，并发送一条消息以检索客户数据。服务器处理该请求并通过 WebSocket 连接持续发送数据。

使用 JSON 响应

无论使用 AJAX 还是 Web Sockets，使用 JSON 作为响应格式是一个明智的选择。JSON 是一种轻量级的文本格式，便于解析和处理客户端端。服务器端代码应将数据库数据转换为 JSON 对象，然后将其作为响应返回。

实战案例

任务：创建一个用户列表页面，该页面从数据库动态获取用户数据并显示。

步骤：

创建一个 get_users.php 文件，该文件用于从数据库中获取用户数据并将其编码为 JSON：

<?php
$servername = "localhost";
$username = "root";
$password = "";
$dbname = "myDB";

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

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

// 将结果编码为 JSON
$users = array();
while ($row = $result->fetch_assoc()) {
  $users[] = $row;
}
echo json_encode($users);
?>

在 HTML 页面中使用 AJAX 调用检索用户数据并将其显示：

<script>
  function getUsers() {
    var xhr = new XMLHttpRequest();
    xhr.open("GET", "get_users.php");
    xhr.onload = function() {
      if (xhr.status === 200) {
        var users = JSON.parse(xhr.responseText);
        displayUsers(users);
      } else {
        alert("Error fetching users.");
      }
    };
    xhr.send();
  }
</script>

<body onload="getUsers()">
  <div id="user-list"></div>
</body>

在 HTML 页面中创建 displayUsers() 函数以显示用户数据。

通过遵循这些步骤，你将创建出利用 HTML 从数据库动态读取数据的用户列表页面。

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