查询提交表单后的问题

<form action="?action=search" method="post" name="form1" id="form1">

<p>物料名称：

  <input name="txtName" type="text" id="txtName" value="" />

   类别：  

  <select name="sltCategory" id="sltCategory" onchange="document.getElementById('txtCategory').value=document.getElementById('sltCategory').value">

  	<option value="">无</option>

    <option value="0">耗材</option>

    <option value="1">电脑</option>

    <option value="2">其他设备</option>

  </select><input name="txtCategory" type="text" id="txtCategory" size="10" value="0,1,2"   />

   <input name="btnSearch" type="submit" id="btnSearch" value=" 查询 " />

</form>

<?php 

	$class = 'action=search&txtName='.$_REQUEST['txtName'].'&txtCategory='.$_REQUEST['txtCategory'];

	echo $class."<br>";

	if($_REQUEST['txtName']&&$_REQUEST['action']=="search"){ 

		$name = $_REQUEST['txtName']; 

		$category = $_REQUEST['txtCategory'];		

		if($name == null){

			$sql = "select * from material where Mat_category in ($category) order by Mat_id";

		}else

			$sql= "select * from material where Mat_name like '%$name%' and Mat_category in ($category)";

	}else{

			$sql = "select * from material order by Mat_id";				

	}

	echo $sql;

	

	$page = page($db,$sql,5,$class);

	while($row=mysql_fetch_array($page[0])){

?>