How to implement three-level linkage in ajax php-PHP Problem-php.cn

Ajax PHP method to implement three-level linkage: first create a test database and create three tables; then initialize all provinces; then pass the current province ID to the server program through an ajax request; finally Just query the database and perform necessary processing and display.

How to implement three-level linkage in ajax php

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The case involves database and database design As follows:

First create a test database with the following content:

CREATE TABLE IF NOT EXISTS `province` (
  `province_id` int(2) NOT NULL AUTO_INCREMENT,
  `province_name` varchar(20) NOT NULL,
  PRIMARY KEY (`province_id`)
) ENGINE=InnoDB  DEFAULT CHARSET=utf8 AUTO_INCREMENT=3 ;
 
INSERT INTO `province` (`province_id`, `province_name`) VALUES
(1, &#39;安徽&#39;),
(2, &#39;浙江&#39;);
 
CREATE TABLE IF NOT EXISTS `city` (
  `city_id` int(4) NOT NULL AUTO_INCREMENT,
  `city_name` varchar(20) NOT NULL,
  `province_id` int(4) NOT NULL,
  PRIMARY KEY (`city_id`)
) ENGINE=InnoDB  DEFAULT CHARSET=utf8 AUTO_INCREMENT=5 ;
 
INSERT INTO `city` (`city_id`, `city_name`, `province_id`) VALUES
(1, &#39;合肥&#39;, 1),
(2, &#39;安庆&#39;, 1),
(3, &#39;南京&#39;, 2),
(4, &#39;徐州&#39;, 2);
 
CREATE TABLE IF NOT EXISTS `county` (
  `county_id` int(4) NOT NULL AUTO_INCREMENT,
  `county_name` varchar(20) NOT NULL,
  `city_id` int(4) NOT NULL,
  PRIMARY KEY (`county_id`)
) ENGINE=InnoDB  DEFAULT CHARSET=utf8 AUTO_INCREMENT=5 ;
 
INSERT INTO `county` (`county_id`, `county_name`, `city_id`) VALUES
(1, &#39;怀宁&#39;, 2),
(2, &#39;望江&#39;, 2),
(3, &#39;肥东&#39;, 1),
(4, &#39;肥西&#39;, 1);

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Description of the database: I created three tables, namely province, city, and county, and inserted several test data. Of course, you can also design Of course, the efficiency of a table is not as good as that of a table, so it is not recommended to use it. It depends on your personal habits.

The implementation process is not difficult, the idea is as follows:

1) Initialize all provinces, this can be done directly from the database Query the province
2) When the user selects a province, an event is triggered and the id of the current province is triggered. Issuing a request through ajax and passing it to the server program
3) Server According to the client's request, query the database and return it to the client in a certain format
## 4) The client obtains the data from the server and performs necessary The processing is displayed

Createselect.php (The code is simple, it just implements the function, just explain the principle!)

1 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
2 <html>
3 <head>
4 <title>三级联动(作者：mckee - www.phpddt.com)</title>
5 <meta http-equiv="content-type"content="text/html; charset=UTF-8"/>
6 <script>
7 function createAjax(){
8 var xmlHttp = false;
9 if (window.XMLHttpRequest){
10 xmlHttp = new XMLHttpRequest();
11 }else if(window.ActiveXObject){
12 try{
13 xmlHttp = new ActiveXObject("Msxml2.XMLHTTP");
14 }catch(e){
15 try{
16 xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
17 }catch(e){
18 xmlHttp = false;
19 }
20 }
21 }
22 return xmlHttp; 
23 }
24 
25 var ajax = null;
26 function getCity(province_id){
27 ajax = createAjax();
28 ajax.onreadystatechange=function(){
29 if(ajax.readyState == 4){
30 if(ajax.status == 200){ 
31 var cities = ajax.responseXML.getElementsByTagName("city");
32 $(&#39;city&#39;).length = 0;
33 var myoption = document.createElement("option");
34 myoption.value = "";
35 myoption.innerText = "--请选择城市--";
36 $(&#39;city&#39;).appendChild(myoption);
37 for(var i=0;i<cities.length;i++){
38 var city_id = cities[i].childNodes[0].childNodes[0].nodeValue;
39 var city_name = cities[i].childNodes[1].childNodes[0].nodeValue;
40 var myoption = document.createElement("option");
41 myoption.value = city_id;
42 myoption.innerText = city_name;
43 $(&#39;city&#39;).appendChild(myoption);
44 }
45 }
46 }
47 }
48  
49 ajax.open("post","selectPro.php",true);
50 ajax.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
51 ajax.send("province_id="+province_id);
52  
53 }
54  
55 function getCounty(city_id){
56 ajax = createAjax();
57 ajax.onreadystatechange=function(){
58 if(ajax.readyState == 4){
59 if(ajax.status == 200){
60  
61 var cities = ajax.responseXML.getElementsByTagName("county");
62 $(&#39;county&#39;).length = 0;
63 var myoption = document.createElement("option");
64 myoption.value = "";
65 myoption.innerText = "--请选择县--";
66 $(&#39;county&#39;).appendChild(myoption);
67 for(var i=0;i<cities.length;i++){
68 var city_id = cities[i].childNodes[0].childNodes[0].nodeValue;
69 var city_name = cities[i].childNodes[1].childNodes[0].nodeValue;
70 var myoption = document.createElement("option");
71 myoption.value = city_id;
72 myoption.innerText = city_name;
73 $(&#39;county&#39;).appendChild(myoption);
74 }
75 }
76 }
77 }
78 ajax.open("post","selectPro.php",true);
79 ajax.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
80 ajax.send("city_id="+city_id);
81 }
82  
83 function $(id){
84 return document.getElementById(id);
85 }
86  
87 </script>
88 </head> 
89 <body>
90 <form name="location">
91 <select name="province" onchange="getCity(this.value)">
92 <option value="">-- 请选择省份--</option>
93 <?php
94 $conn = mysql_connect("localhost","root","");
95 mysql_select_db("test");
96 mysql_query("set names utf8");
97 $sql = "select * from province"; 
98 $result = mysql_query( $sql ); 
99 while($res = mysql_fetch_assoc($result)){ 
100 ?> 
101 <option value="<?php echo $res[&#39;province_id&#39;]; ?>"><?php echo $res[&#39;province_name&#39;]?></option> 
102 <?php
103 } 
104 ?>
105 </select>
106  
107 <select name="city" id="city" onChange="getCounty(this.value)">
108 <option value="">--请选择城市--</option>
109 </select>
110  
111 <select name="county" id="county">
112 <option value="">--请选择县--</option>
113 </select>
114 </form>
115 </body>
116 </html>

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CreateselectPro.phpPage:

117 <?php
118 //禁止缓存(www.phpddt.com原创)
119 header("Content-type:text/xml; charset=utf-8");
120 header("Cache-Control:no-cache");
121 //数据库连接
122 $conn = mysql_connect("localhost","root","");
123 mysql_select_db("test");
124 mysql_query("set names utf8");
125 
126 if(!empty($_POST[&#39;province_id&#39;])){
127 
128 $province_id = $_POST[&#39;province_id&#39;];
129 $sql = "select * from city where province_id = {$province_id}";
130 $query = mysql_query($sql);
131 $info = "<province>";
132 while($res = mysql_fetch_assoc($query)){
133 $info .= "<city>";
134 $info .= "<city_id>".$res[&#39;city_id&#39;]."</city_id>";
135 $info .= "<city_name>".$res[&#39;city_name&#39;]."</city_name>";
136 $info .= "</city>";
137 }
138 $info .= "</province>";
139 echo $info;
140 }
141 
142 if(!empty($_POST[&#39;city_id&#39;])){
143 
144 $city_id = $_POST[&#39;city_id&#39;];
145 $sql = "select * from county where city_id = {$city_id}";
146 $query = mysql_query($sql);
147 $info = "<city>";
148 while($res = mysql_fetch_assoc($query)){
149 $info .= "<county>";
150 $info .= "<county_id>".$res[&#39;county_id&#39;]."</county_id>";
151 $info .= "<county_name>".$res[&#39;county_name&#39;]."</county_name>";
152 $info .= "</county>";
153 }
154 $info .= "</city>";
155 echo $info;
156 }
157 ?>

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The interface is as follows:

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