php问题里的post使用问题

我的htm表单
<form action="studnet3.php" method="post">
<select name="xb">
<option value="0">全体学生</option>
<option value="1">男学生</option>
<option value="2">女学生</option>
</select>
<input type="submit" value="提交">

</form>

我的student3.php
<?php
$xh=array("学号","072188135","072188136","072188145","07218137");
$xm=array("姓名","小刘","小张","小花","小黄");
$zh=array("座号","26","27","28","38");
$nl=array("年龄","20","20","22","20");
$xb=array("性别","男","女","男","女");
print '<table border="1">';