การทำ Search ไม่ยอมทำงานครับ เวลากดเเล้ว จะไม่สามารถ Search ได้ครับ คือการแสดงผล

<form id="form1" name="form1" method="post" action="login.php?action=admin">
ค้นหา <input name="txt_search" type="text" value="<?=$_POST['txt_search']?>" /> <input name="Search" type="submit" value="ค้นหา" />

 <input name="Search2" type="submit" value="Total" />
</form>      

 <?
  $sql_show = "select * from service";
  if($_POST['Search'])
  {
  	$txt_search = $_POST['txt_search'];
  	$sql_show.=" where name like '%$txt_search%' or position like '%$txt_search%' ";
  }
  $result_show = mysql_query($sql_show) or die(mysql_error());
  ?>
  
<table width="100%" border="0" cellspacing="1" cellpadding="2">  
                      <tr bgcolor="#BDBFB9">
                        <td align="center" width="3%">ID</td>
                        <td align="left" width="18%">name</td>
                        <td align="left" width="27%">profile</td>
                        <td align="left" width="18%">detail</td>
                        <td align="center" width="15%">comment</td>
                        <td align="center" width="13%">status</td>
                        <td align="center" width="6%">Method</td>
                      </tr>
<?
while($r = mysql_fetch_array($result_show)){
($bg=="#F9F9F9") ? $bg="#E6E6E6" : $bg="#F9F9F9" ;
if($r['status']=="Y") $bg="#D7F2FF";
?>					
                      <tr bgcolor="<?=$bg?>" valign="top">
                        <td height="81" align="center" style="text-align: left"><?=$r['id']?></td>
                        <td align="center" style="text-align: left"><? echo utf8totis620(StripSlashes($r['name']))?></td>
                        <td align="left" style="text-align: left">แผนก:<? echo utf8totis620(StripSlashes($r['position']))?><br>
                          ชั้น :
                          <? echo StripSlashes($r['class'])?><br>                          
                          อีเมล:<? echo StripSlashes($r['mail'])?><br>
                          เบอร์:<? echo StripSlashes($r['phone'])?><br>
                        เวลา:<? echo StripSlashes($r['date_create'])?></td>
                        <td align="left" style="text-align: left"><? echo utf8totis620(StripSlashes($r['detail']))?></td>
                        <td align="center">&nbsp;</td>
                        <td align="center"><select onChange="if(confirm('กด OK เพื่อเปลี่ยนสถานะ')) window.location='<?=basename($PHP_SELF)?>?action=status&id=<?=$r['id']?>&status='+this.value;">
							<option value="Y" <?if($r['status']=="Y") echo "selected";?>>แสดง</option>
							<option value="N" <?if($r['status']=="N") echo "selected";?>>ไม่แสดง</option>
						</select></td>
                        <td align="center">
                        <A HREF="javascript:;" onClick="if(confirm('กด OK เพื่อลบ')) window.location='<?=basename($PHP_SELF)?>?action=delete&id=<?=$r['id']?>';">ลบ</A>
                        &nbsp;</td>
  </tr> 
<?
} 
?>
</table>

<?
}	

break;
default;

}	
?>

echo $sql_show;
$result_show = mysql_query($sql_show) or die(mysql_error());

$txt_search = $_POST['txt_search'];
if($txt_search==""){
$sql_show = "select * from service";
}else{
$sql_show = "select * from service where name like '%$txt_search%' or position like '%$txt_search%' ";
}
$result_show = mysql_query($sql_show) or die(mysql_error());

CREATE TABLE `service` (
  `id` int(11) NOT NULL auto_increment,
  `name` varchar(255) NOT NULL,
  `position` varchar(255) NOT NULL,
  `class` varchar(3) NOT NULL,
  `detail` text NOT NULL,
  `comment` varchar(255) NOT NULL,
  `phone` varchar(30) NOT NULL,
  `mail` varchar(100) NOT NULL,
  `date_create` datetime NOT NULL,
  `status` varchar(2) NOT NULL default 'N',
  `note` varchar(255) NOT NULL,
  PRIMARY KEY  (`id`)
) ENGINE=MyISAM  DEFAULT CHARSET=utf8 AUTO_INCREMENT=96 ;