다중검색 기능을 만들고 있는데 post 로 값을 넘겨둔 뒤에도 select 값을 남겨두고 싶습니다. 채택완료

</p>

<p><form method="post">

<table>

    <tr>

     <th>

      <label class="control-label" for="">지역</label>

     </th>

     <td class="address_box">

      <select class="form-control mgb" name="sido" id="sido"></select>

      <select class="form-control" name="gugun" id="gugun"></select>

      <select class="form-control mgb" name="dong" id="dong"></select>

     </td>

    </tr>

</table>

<input type="submit">

</form></p>

<p>

<script src="<a href="http://code.jquery.com/jquery-latest.min.js"></script>" target="_blank" rel="noopener noreferrer">http://code.jquery.com/jquery-latest.min.js"></script></a>

<script>

function sojaeji(sido, gugun, dong) {

 var

 addr ={

 '시도' : ['선택','서울','부산','대구','인천','광주','대전','울산','강원','경기','경남','경북','전남','전북','제주','충남','충북'],

 '선택' : [],

  '서울' : ['강남구','강동구','강북구','강서구','관악구','광진구','구로구','금천구','노원구','도봉구','동대문구','동작구','마포구','서대문구','서초구','성동구','성북구','송파구','양천구','영등포구','용산구','은평구','종로구','중구','중랑구'],

  '강남구': ['논현동', '신사동'],

  '서대문구': ['연희동', '창천동']

//...

};</p>

<p>this.sido = document.getElementById('sido');

 this.gugun = document.getElementById('gugun');

 this.dong = document.getElementById('dong');

 var parent = this;</p>

<p> makeOption('시도', this.sido);</p>

<p> if (sido) this.sido.value = sido;</p>

<p> if (gugun) {

  makeOption(sido, this.gugun);

  this.gugun.value = gugun;

 }</p>

<p> if (dong) {

  // makeOption(sido + '->' + gugun,  this.dong);

  makeOption(gugun,  this.dong);

  this.dong.value = dong;

 }</p>

<p> this.sido.onchange = function() {

  if(this.value == "선택"){

   $("#gugun").html("");

   $("#dong").html("");

  }else{

   makeOption(this.value, parent.gugun);

   // makeOption(this.value + '->' + parent.gugun.value, parent.dong);

   makeOption(parent.gugun.value, parent.dong);

  }

 };</p>

<p> this.gugun.onchange = function() {

  // makeOption(parent.sido.value + '->' + this.value, parent.dong);

  makeOption(this.value, parent.dong);

 };</p>

<p> function makeOption(idx, obj) {

  var html = '', i=0;

  for (; i<addr[idx].length; i++) html += '<option value="'+addr[idx][i]+'">'+addr[idx][i]+'</option>';

  obj.innerHTML = html;

 }

}</p>

<p>

<?php

$sido = isset($_POST['sido']) ? $_POST['sido'] : '';

$gugun = isset($_POST['gugun']) ? $_POST['gugun'] : '';

$dong = isset($_POST['dong']) ? $_POST['dong'] : '';</p>

<p>$jsvars = "var sido = '{$sido}', gugun = '{$gugun}', dong = '{$dong}';";

echo $jsvars;

?></p>

<p>// var sido = '서울', gugun = '서대문구', dong = '창천동';</p>

<p>new sojaeji(sido, gugun, dong);

</script></p>

<p>