php 二级联动菜单

<?php
//PHP部分:
  //取得下拉联动数据
  require("conn.php");
  $result=mysql_query("SELECT * FROM units LEFT JOIN users ON (users.unit=units.unid)");
  $mx=mysql_num_rows($result);

  for ($i=0;$i<$mx;$i++) {
  $r=mysql_fetch_array($result);
  $uname=$r['uname'];
  $unid =$r['unid'];
  $usname=$r['username'];
  $usid=$r['userid'];

  if ($lasun!=$uname) {
  $java1=$java1 . ""$uname",";
  $java2=$java2 . ""$unid",";
  $lasun=$uname;
  if ($i>0) {
  $java3=$java3 . "],[";
  $java4=$java4 . "],[";
  }
  } else {
  $java3=$java3 . ",";
  $java4=$java4 . ",";
  }

  $java3= $java3 . ""$usname"";
  $java4= $java4 . ""$usid"";

  }

  $java1="[" . substr_replace($java1,"",-1) . "]n";
  $java2="[" . substr_replace($java2,"",-1) . "]n";
  $java3="[[" . $java3 . "]]n";
  $java4="[[" . $java4 . "]]n";

  //javascript部分
  ?>
  <SCRIPT LANGUAGE="JavaScript" DEFER>
  var fMenu = <?=$java1?>
  var fValue = <?=$java2?>
  var sMenu = <?=$java3?>
  var sValue = <?=$java4?>

  var oWhere = document.all.tar;
  var ofMenu = document.createElement("<SELECT name='unid'>");
  var osMenu = document.createElement("<SELECT name='usid'>");
  with(oWhere)appendChild(ofMenu),appendChild(osMenu);

  createMainOptions();
  createSubOptions(0);

  ofMenu.onchange = function() {createSubOptions(this.selectedIndex);};

  function createMainOptions() {
      for(var i=0;i<fMenu.length;i++)ofMenu.options[i] = new Option(fMenu[i],fValue[i]);
  }
  function createSubOptions(j) {
      with(osMenu) {
               length=0;
               for(var i=0;i<sMenu[j].length;i++)osMenu.options[i] = new Option(sMenu[j][i],sValue[j][i]);
      }
  }

  function checkuser() {
  if (document.forms[1].elements[1].value=="") { alert("没有选择用户"); return false; }
  }
  </SCRIPT>

  
  <div id="tar" style="display:inline"></div>
  <!--
  另外附users和units数据表结构
  表users:
  userid
  username
  unit

  表units:
  unid
  uname

补充：Php教程,Php常用代码