<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>菜鳥教程(runoob.com)</title>
<script src="https://cdn.staticfile.org/jquery/1.10.2/jquery.min.js">
</script>
<script>
$(document).ready(function(){
$("#sele").change(function(){
var p1=$("#sele").find("option:selected").text();
$("#a").empty();
$("#a").append(p1*1);
});
});
</script>
</head>
<body>
<?php $a= 20;?>
<select id="sele">
<option name="1">1</option>
<option name="2">2</option>
<option name="3">3</option>
<option name="4">4</option>
<option name="5">5</option>
<option name="6">6</option>
<option name="7">7</option>
<option name="8">8</option>
</select>
<div id="a">1</div>
</body>
</html>