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Detailed explanation of the basics and login steps of Ajax

php中世界最好的语言Original: 2018-04-02 11:29:101242browse

This time I will bring you a detailed explanation of the basics and login steps of Ajax. What are the basics and login of Ajax? What are the precautions? The following is a practical case, let's take a look.

Ajax is the abbreviation of Asynchronous

JavaScript and XML.

Advantages of Ajax:

Advantages: reduce the burden on the server, fetch data on demand, and minimize redundant requests

Partially refresh the page, reduce user psychology and actual waiting time, and bring better user experience

Based on xml standardization and widely supported, no need to install plug-ins, etc.

Further Promote the separation of pages and data

Ajax includes the following technologies:

Based on web standards (standards-based presentation) XHTML+CSS representation;

Use DOM (

Document Object Model) for dynamic display and interaction;

Use XML and XSLT for data exchange and related operations;

Use XMLHttpRequest Perform asynchronous data query and retrieval;

Use JavaScript to bind everything together.

In other words, the biggest feature of Ajax is that it can achieve dynamic without refreshing

Using Ajax:

Example:

A table in the database:

Click to see if the user name is available:

Main page code:

<!DOCTYPE html>
<html>
  <head>
    <meta charset="UTF-8">
    <title></title>
    <script src="jquery-1.11.2.min.js"></script>
  </head>
  <body>
    输入一个用户名：<input type="text" id="zhang" />
    <span id="tishi"></span>
  </body>
</html>
<script>
  //给文本框加上事件
  $("#zhang").blur(function(){
    //1取内容
    var zhang = $(this).val();
    //val取到表单元素、给变量
    //2将取到的内容内容区数据库验证
    //调用Ajax
    $.ajax({
      type:"POST",
      //提交方式
      url:"chuli.php",
      //请求哪一个php文件（请求地址）
      data:{yhm:zhang},
      //给zhang取名yhm，传过去，是一个json
      //请求处理页面需不需要传数据过去，不需要传不用写
      dataType:"TEXT",
      //处理页面返回的类型:TEXT字符串 JSON,JSON，XML，只有三种类型
      success:function(data){
        //回调函数
//        data为返回的值
        //成功之后要调用的函数
        if(data==0)
        {
          //如果为0
          $("#tishi").text("该用户名为0；可用！");
          $("#tishi").css("color","green");
        }
        else
        {
          $("#tishi").text("该用户名已存在；不可用！");
          $("#tishi").css("color","brown");
        }
      }
    });
    //3给出提示
  })
</script>

Next, do the processing page:

<?php
$zhang = $_POST["yhm"];
//取值
include("db.class.php");
$db = new db();
$sql = "select count(*) from mydb where zhang = &#39;{$zhang}&#39;";
$arr = $db->Query($sql);
echo $arr[0][0];
//直接输出相当于返回
?>

Picture:

Enter an existing user name:

Enter a non-existent user name ：

Write another login:

The code of the login page:

<!DOCTYPE html>
<html>
<head>
  <meta charset="UTF-8">
  <title></title>
  <script src="jquery-1.11.2.min.js"></script>
</head>
<body>
<h1>登入页面</h1>
<p>帐号<input type="text" id="zhang"/></p>
<p>密码<input type="text" id="mi"/></p>
<input type="button" id="btn" value="登入"/>
</body>
</html>
<script>
  $("#btn").click(function(){
    //1取数据
    var zhang = $("#zhang").val();
    var mi = $("#mi").val();
    //2验证数据
    $.ajax({
      url:"drcl.php",
      data:{zhang:zhang,mi:mi},
      type:"POST",
      dataType:"TEXT",
      success:function (data) {
        //回调函数
        //判断返回值
        if(data=="ok")
        {
          window.location.href = "zym.php";
        }
        else
        {
          alert("用户名或密码错误");
        }
      }
    });
    //提示
  })
</script>

The next step is the login processing page:

<?php
include ("db.class.php");
$db = new db();
$zhang = $_POST["zhang"];
$mi = $_POST["mi"];
//取值
$sql = "select mi from mydb WHERE zhang = &#39;{$zhang}&#39;";
$arr = $db->Query($sql);
if($arr[0][0]==$mi && !empty($mi))
{
  echo "ok";
}
else
  {
    echo "no";
  }
?>

Take a look at the picture. If the input is incorrect, it will prompt directly on this page:

If the input is correct, it will jump:

The advantage of using Ajax to write login is that you don’t have to jump to another page when an error is prompted.

I believe you have mastered the method after reading the case in this article. For more exciting information, please pay attention to other related articles on the php Chinese website!

Detailed explanation of the basics and login steps of Ajax

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