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<!DOCTYPE html><html lang="en"><head> ???<meta charset="UTF-8"> ???<meta name="viewport" content="width=device-width, initial-scale=1.0"> ???<meta http-equiv="X-UA-Compatible" content="ie=edge"> ???<title>PHP+ajax实现二级联动</title></head><body> ???<select id="province"> ???????<option value="0">请选择省份</option> ???????<option value="1">北京</option> ???????<option value="2">河北</option> ???????<option value="3">山东</option> ???</select> ???<select id="city"> ???????<option value="0">请选择城市</option> ???</select></body><script src="https://code.jquery.com/jquery-3.3.1.min.js"></script><script>$(function(){ ???$("#province").change(function(){ ???????var province = $(this).val(); // 获取province的value值 ???????if(province == 0){ ???????????// province为0的时候停止；否则 ???????????return; ???????}else{ ???????????var url = ‘demo.php‘; ???????????$.ajax({ ???????????????url: url, ????????????// php的url路径 ???????????????type: ‘post‘, ???????????????data: {province:province}, ???????????????dataType: ‘json‘, ???????????????success: function(res) { ???????????????????if(res.code == 200){ ???????????????????????var option = ‘<option>请选择城市</option>‘; ???????????????????????var list = res.list; ???????????????????????for (var i = 0; i < list.length; i++) { ??// 循环返回的值（城市） ???????????????????????????option += "<option>" + list[i] + "</option>"; ???????????????????????} ???????????????????}else{ ???????????????????????var option = ‘<option>请选择城市</option>‘; ?// 请求失败（默认） ???????????????????} ???????????????????$("#city").html(option); ???// js刷新第二个下拉框的值 ???????????????} ???????????}) ???????} ???})})</script></html>
接下来为PHP代码，注释已表明；
?<?php$province = $_POST[‘province‘]; ??????// 获取ajax传来的值$list[‘1‘] = [‘朝阳‘, ‘海淀‘, ‘西城‘];$list[‘2‘] = [‘保定‘, ‘唐山‘, ‘邯郸‘];$list[‘3‘] = [‘济南‘, ‘菏泽‘, ‘日照‘];if($list[$province]){ ????????????????// 数组存在值的情况下 ???echo json_encode([‘code‘=>200, ‘list‘=>$list[$province]]); ?// 200成功，$list[$province]传递相应的数据}else{ ???echo json_encode([‘code‘=>500]);}?
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PHP+ajax实现二级联动
原文地址：https://www.cnblogs.com/xiaocong-PHP-12685/p/10569772.html