ทำ text ค้นหากระทู้โดยใช้ keyword แต่เมื่อพิมในช่องค้นหาแล้วทำไม่ค้นหาไม่เจอค่ะ

  <p><a href="add_web.php">New Post</a></p>
    <table width="200" height="211" border="0">
      <tr>
        <td><form id="form2" name="form2" method="post" action="index.php">
          <table width="767" border="0">
            <tr>
              <td colspan="5"><table width="291" border="0" align="center">
                  <tr>
                    <td width="177"><div align="center">
                        <input type="text" name="keyword" value="<? echo"$keyword"; ?>" />
                    </div></td>
                    <td width="98"><input type="submit" name="button2" id="summit" value="ค้นหากระทู้" />
                    </td>
                  </tr>
              </table></td>
            </tr>
            <tr>
              <td colspan="5">&nbsp;</td>
            </tr>
            <tr>
              <td width="216"><div align="center">หัวข้อคำถาม</div></td>
              <td width="98"><div align="center">ผู้ตั้งคำถาม</div></td>
              <td width="105"><div align="center">ตั้งเมื่อวันที่</div></td>
              <td width="120"><div align="center">จำนวนผู้ตอบ</div></td>
              <td width="206"><div align="center">ตอบล่าสุด</div></td>
            </tr>
            <?
include("../include/conf.php");
$sql="select * from tb_webboard";
$db_query=mysql_query($sql);
$num = mysql_num_rows($db_query);

//$a=0;
//while($a<$num){
//$result = mysql_fetch_array($db_query);
while($result = mysql_fetch_array($db_query)){
$id_webboard = $result['id_webboard'];
$sql1="select * from tb_ans where ref_idweb ='$id_webboard'";
//echo $sql1;
//exit ();
$db_query1=mysql_query($sql1);
$numa = mysql_num_rows($db_query1);

$result1=mysql_fetch_array($db_query1);

$sqlnamepost="SELECT * FROM tb_ans WHERE ref_idweb = '$id_webboard' order by id_ans desc limit 1";
$db_queryname=mysql_query($sqlnamepost);
$resultname=mysql_fetch_array($db_queryname);


?>
            <tr>
              <td><div align="center"><a href='show_web.php?id_webboard=<?=$id_webboard;?>'>
                  <?=$result['title'];?>
              </a></div></td>
              <td><div align="center">
                  <?=$result['name'];?>
              </div></td>
              <td><div align="center">
                  <?=$result['date'];?>
              </div></td>
              <td><div align="center">
                  <?=$numa;?>
              </div></td>
              <td><p align="left">โดย
                    <?=$resultname['name_ans'];?>
                วันที่
                <?=$result['date'];?>
              </p></td>
            </tr>
            <tr>
              <td colspan="5">&nbsp;</td>
            </tr>
            <tr>
              <td colspan="5"><?
if($fields==""){
}else{
include("../include/conf.php") ;
if($fields=="title"){
$sql2="SELECT * FROM tb_webboard where title=$fields"; 
$db_query2=mysql_db_query($db,$sql2);
$result2 = mysql_fetch_array($db_query2);
$keyword = $result2[id_webboard];
}
$sql="SELECT * FROM tb_webboard where $fields=$fields"; 
$db_query=mysql_db_query($db,$sql);
$num_rows=mysql_num_rows($db_query); /* นับ Reccord ที่พบ */
$a=0;
while($a < $num_rows)
{
$result = mysql_fetch_array($db_query);
$id_webboard = $result[id_webboard];
$title = $result[title];
$detail= $result['detail'];
$name = $result[name];
$date = $result[date];
if($status_log=="1"){
if ($a % 2 == 0){
?></td>
            </tr>
            <?
//$a++;
}
?>
          </table>
                <table width="766" border="0">
                  <tr>
                    <td colspan="5"><div align="left">
                        <?
include("../include/conf.php");
$sql="select * from tb_webboard where id_webboard like '%$keyword%'";
$db_query=mysql_db_query($db,$sql);
$result = mysql_fetch_array($db_query);
$id_webboard = $result[id_webboard];
$title = $result[title];
$detail = $result[detail];
$name = $result[name];
$date = $result[date];
?>
                      </div>
                        <div align="center"></div>
                      <div align="center"></div></td>
                  </tr>
                  <tr>
                    <td width="218"><div align="center">หัวข้อคำถาม</div></td>
                    <td width="100"><div align="center">ผู้ตั้งคำถาม</div></td>
                    <td width="104"><div align="center">ตั้งเมื่อวันที่</div></td>
                    <td width="116"><div align="center">จำนวนผู้ตอบ</div></td>
                    <td width="206"><div align="center">ตอบล่าสุด</div></td>
                  </tr>
                  <tr>
                    <td><div align="center"><a href='index.php?id_webboard=<?=$id_webboard;?>'>
                        <?=$result['title'];?>
                    </a></div></td>
                    <td><div align="center">
                        <?=$result['name'];?>
                    </div></td>
                    <td><div align="center">
                        <?=$result['date'];?>
                    </div></td>
                    <td><div align="center">
                        <?=$numa;?>
                    </div></td>
                    <td>โดย
                      <?=$resultname['name_ans'];?>
                      วันที่
                      <?=$result['date'];?></td>
                  </tr>
                  <tr>
                    <td colspan="5"><?
					}
else {
?>
                        <?
	}
}
$a++;
}
}
?>