的JavaScript
// JQuery script is on ajax.php page
// JQUERY PIECE TO PROCESS STATE AND CITY VALUES
// BASED ON COUNTRY SELECTION
function change_CountryNo() {
var xmlhttp = new XMLHttpRequest();
xmlhttp.open("GET", "ajax.php?CountryNo=" + document.getElementById("CountryNodd").value, false);
xmlhttp.send(null);
document.getElementById("StateID").innerHTML = xmlhttp.responseText;
if (document.getElementById("CountryNodd").value == "CountryNo") {
document.getElementById("CityID").innerHTML = "<select><option>City</option></select>";
}
}
function change_StateID() {
var xmlhttp = new XMLHttpRequest();
xmlhttp.open("GET", "ajax.php?StateID=" + document.getElementById("StateIDdd").value, false);
xmlhttp.send(null);
document.getElementById("CityID").innerHTML = xmlhttp.responseText;
if (getElementById("StateIDdd").value == "StateID") {
document.getElementById("CityID").innerHTML = "<select><option>City</option></select>";
}
}
<!DOCTYPE html>
<html>
<head>
<!-- index.php -->
<!-- THIS CODE PROVIDES A DROP DOWN FORM
FOR USER TO SELECT COUNTRY THEN STATE THEN CITY
A JQUERY SCRIPT PROCESSES THE COUNTRY VALUE
TO PRODUCE THE APPROPRIATE STATES AND
PROCESSES THE STATE VALUE TO PRODUCE
THE APPROPRIATE CITIES -->
<title>Country, State, City Selection</title>
<link href="https://fonts.googleapis.com/css?family=Open+Sans" rel="stylesheet">
<link rel="stylesheet" href="http://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css">
<link rel="stylesheet" type="text/css" href="css/styles.css">
</head>
<body>
<!-- THESE FILES ARE DATABASE CONNECTION AND FUNCTIONS
FOR VARIOUS LOGIN, USER SESSION VARIABLES TO IDENTIFY
THE CONTACT NO OF USER UPDATING THEIR LOCATION -->
<?php include("includes/header.php") ?>
<?php include("includes/nav.php") ?>
<?php //Check user's login status
if (logged_in() === false) {
echo "Redirecting...";
redirect("../index.html");
}
?>
<!-- responsive setup for form -->
<div class="row">
<div class="col-lg-6 col-lg-offset-3">
</div>
</div>
<!-- end of class row div -->
<div class="row">
<div class="col-md-6 col-md-offset-3">
<div class="panel panel-login">
<div class="panel-heading">
<div class="row">
<div class="col-xs-12">
<div class="col-xs-6">
</div>
<div class="col-xs-6">
<a href="Country-State-City.php" class="active" id="">Country-State-City Selection</a>
</div>
</div>
<hr>
</div>
<!-- end of class row div -->
<div class="panel-body">
<div class="row col-md-12" style="text-align: center">
<form method="POST" action="<?php echo htmlspecialchars($_SERVER[" PHP_SELF "]);?>" autocomplete="off">
<div id="CountryNo" class="col-xs-3 form-group" style="font-size: 75%">
<select id="CountryNodd" name="CountryNodd" onChange="change_CountryNo()" class="form-control selectpicker" style="width:100%;">
<option>Country</option>
<?php
$res=mysqli_query($con, "SELECT * FROM countries ORDER BY Country_Descrip");
while($row=mysqli_fetch_array($res))
{
?>
<option value="<?php echo $row["CountryNo"]; ?>"><?php echo $row["Country_Descrip"]; ?></option>
<?php $CountryNodd = $_POST["CountryNo"]; ?>
<?php }
?>
</select>
</div>
<div id="StateID" class="col-xs-3 form-group" style="font-size: 75%">
<select id="StateIDdd" name="StateID" class="form-control selectpicker" style="width:100%;">
<option>Product</option>
</select>
</div>
<div id="CityID" class="col-xs-3 form-group" style="font-size: 75%">
<select id="CityIDdd" name="CityIDdd" class="form-control selectpicker" style="width:100%;">
<option>Brand</option>
</select>
</div>
<div class="form-group">
<img src="img\..." class="img-responsive" alt="Country-State-City Image" width="100%" height="auto">
<div class="col-lg-12 text-center">
<br>
<input type="submit" name="reset" id="reset" tabindex="3" class="form-control btn btn-register" value="Reset Country-State-City Selections" required>
</div>
</div>
<div class="form-group">
<div class="col-lg-12 text-center">
<br>
<input type="submit" name="Update My Country-State-City" id="update" tabindex="4" class="form-control btn btn-register" value="Update My Country-State-City" required>
</div>
</div>
</form>
<!-- end of form -->
</div>
<!-- end of row col-md-12 div -->
</div>
<!-- end of panel-body div -->
</div>
<!-- end of panel-heading div -->
</div>
<!-- end of panel-login div -->
</div>
<!-- end of col-md-6 col-md-offset-3 div -->
</div>
<!-- end of class row div -->
<!-- ajax.php -->
<!DOCTYPE HTML>
<html>
<head>
<title>ajax.php</title>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.1.1/jquery.min.js"></script>
<?php
//THIS FILE PROCESSES THE JQUERY SELECT BASED ON COUNTRY INPUT AND
//THE STATE INPUT
// Turn off error reporting
error_reporting(0);
$con=mysqli_connect('localhost', 'root', '', 'contact_info');
mysqli_set_charset($con,"utf8");
if (!$con) {
die('Could not connect: ' . mysqli_error());
}
// Get the Country and State Values User Selects
$CountryNo=$_GET["CountryNo"];
$StateID=$_GET["StateID"];
//Check user selection for country and list states
if($CountryNo!="Country")
{
$query="SELECT State_ID, StateCountry_ID, State_Description FROM states WHERE StateCountry_ID=$CountryNo ORDER BY State_Description";
$result=mysqli_query($con, $query);
echo "<select id='StateIDdd' onchange='change_StateID()' selected>";
echo "<option>"; echo "State"; echo "</option>";
while($row=mysqli_fetch_array($result))
{
echo "<option value='$row[State_ID]'>"; echo $row["State_Description"]; echo "</option>";
}
echo "</select>";
}
//Check user selection for state and list cities
if($StateID!="State")
{
$query="SELECT CityID, City_Name, CountryNo, CityState_ID FROM cities WHERE CityState_ID=$StateID ORDER BY City_Name";
$result=mysqli_query($con, $query);
echo "<select>";
while($row=mysqli_fetch_array($result))
{
echo "<option value='$row[CityID]' selected>"; echo $row["City_Name"]; echo "</option>";
}
echo "</select>";
}
?>
<?php include("ajax2.php") //Go to post to MySQL processing
?>
</head>
</html>
<!-- ajax2.php -->
<!-- THIS FILE POSTS THE COUNTRY, STATE, CITY VALUES TO
MYSQLI AND UPDATES THE USER'S CONTACT LOCATION -->
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.1.1/jquery.min.js"></script>
<?php include("includes/header.php") ?>
<?php include("includes/nav.php") ?>
<?
// Turn off error reporting
error_reporting(0);
$con=mysqli_connect('localhost', 'root', '', 'contact_info');
mysqli_set_charset($con,"utf8");
if (!$con) {
die('Could not connect: ' . mysqli_error());
}
?>
<?
// Ensure user is logged in to get values
// for ContactNo
php if (logged_in() === false) {
echo "Redirecting...";
redirect("../index.html");
}
//store country, state, city selection and update contact's location
$CountryNo = $_POST['CountryNodd'];
$StateID = $_POST['StateIDdd'];
$CityID = $_POST['CityIDdd'];
//Update MySQL
$sql = "UPDATE contact_location SET CountryNodd=$CountryNo, StateID=$StateID, CityID=$CityID";
$sql.= "WHERE ContactNo=$ContactNo"; //Contact info is from contact table accessed via function include in header.php
$res_update = mysqli_query($con,$sql);
if($res_update) {
echo "Location updated successfully";
}
else {
echo "Not working...";
}
?>
我已阅读相关问题/回复，但没有解决我的问题。 我是jQuery＆amp;的新手使用MySQL后端进行PHP编程。
在用户处创建了一个3级下拉（国家/州 - 城市）表单 可以选择国家 - 州 - 城市价值，这将更新 MySQL的。
虽然我可以GET和POST国家变量，但我一直都是 国家和城市不成功。我可以看到正确的价值 State变量，但我没有看到City变量的值 此外，我不能POST状态或城市变量：我得到一个 与每个变量关联的变量的“索引未定义”错误。
答案 0 :(得分：0)
已解决：POST执行发生在JavaScript操作之前，这是因为PHP，服务器端，在Java之前执行，客户端。我在城市选择发生时将MySQL更新代码移动到PHP脚本中。
我不会提供代码，因为到目前为止我收到的评论表明我的文档需要工作。当然感谢反馈并将采取措施改进未来的帖子。谢谢！