[PHP]ทำค้นหาหลายเงื่อนไขโดยใช้ List box แต่ลองทำแล้วกลับค้นหาเงื่อนไขเดียว

<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<?php mysql_query("SET NAMES UTF8");?>
<form name="frmSearch" method="get" action="<?php echo $_SERVER['SCRIPT_NAME'];?>">
  <table width="599" border="1" align="center">
    <tr>
      <th>Keyword
        <label for="select1"&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;></label>
        <select name="select" id="select">
	<option value="A1" <? if($Search2=="ID_Card"){ ?>selected<? }?>>รหัส</option>
     	<option value="A2"<? if($Search2=="B_Name"){ ?>selected<? }?>>ชื่อ</option>
        </select>
         <input name="txtKeyword" type="text" id="txtKeyword" value="">
      <input type="submit" value="Search"></th>
    </tr>
  </table>
</form>
<?php
if($_GET["txtKeyword"] != "")
	{
	$objConnect = mysql_connect("localhost","root","1234") or die("Error Connect to Database");
	mysql_query("SET NAMES UTF8");
	$objDB = mysql_select_db("test") or die(mysql_error());
	if($Search2 = "ID_Card" ){
	$strSQL = "select * from businessman where ID_Card like '".$_GET['txtKeyword']."'";
	}elseif($Search2 = "B_Name"){$strSQL = "select * from businessman where B_Name like '".$_GET['txtKeyword']."'";}
	
	$objQuery = mysql_query($strSQL) or die (mysql_error());
	
	ิ
	?>
	<table width="1444" border="1" align="center">
	  <tr>
		<th width="160"> <div align="center">เลขบัตรประชาชน </div></th>
		<th width="79"> <div align="center">ชื่อ-สกุล </div></th>
		
                    
	  </tr>
	<?php
	$objResult = mysql_fetch_array($objQuery);
	{
	?>
	  <tr>
		<td><div align="center"><?php echo $objResult["ID_Card"];?></div></td>
		<td><?php echo $objResult["B_Name"];?></td>
		
	  </tr>
	<?php
	}
	?>
	</table>
	<?php
	mysql_close($objConnect);
}
?>