ขอความช่วยเหลือเกี่ยวกับการ Search like มาแสดงครับ อยากให้แสดงแค่ต้องการ search เท่านั้นครับ

<?php
if(!$_GET['R_ID']){
?>
<div class="col-xs-12 col-sm-6 col-md-8">
<div class="box box-success subject">	
	<div class="box-header with-border subject">
	  <h3 class="box-title">ข้อมูลนักศึกษา</h3>  
	</div>
    <div class="box-body subject">
    
    <form id="form1" name="form1" method="post" action="">
        <div id="custom-search-input">
            <div class="input-group col-md-12">
                <input type="text" class="form-control input-lg" name="search" id="search" placeholder="ค้นหาชื่อ หรือ นามสกุล">
                <span class="input-group-btn">
                    <input type="submit" class="btn btn-info btn-lg" name="button" id="button" value="Search"><i class="glyphicon glyphicon-search"></i>
                </span>
            </div>
        </div>
    </form>
	<table class="table table-striped">
		<tbody>
        <?php
		
		// selecting rows	
			$sno = $row + 1;
			
			if($_POST['search']){
				$search=" where RD_FNAME like '".$_POST['search']."%' or RD_LNAME like '".$_POST['search']."%' or R_TEACHER like '".$_POST['search']."%'";
			}else{
				$search="";
			}
			$sql = "SELECT * FROM tb_register 
			JOIN tb_subject ON (tb_subject.S_ID = tb_register.S_ID)
			JOIN tb_school ON (tb_register.sc_id = tb_school.sc_id)  
			JOIN tb_level ON (tb_level.L_ID = tb_subject.L_ID)".$search;
			$result = mysql_query($sql);
			
			
			while($fetch = mysql_fetch_array($result)){
			$title = $fetch['RD_TITLE'];
			$name = $fetch['RD_FNAME'];
			$lname = $fetch['RD_LNAME'];
			$skill = $fetch['S_NAME'];
			$level = $fetch["L_NAME_S"];
			$std_id = $fetch['RD_SID'];
			$school_id = $fetch['sc_id'];
			$school = $fetch['sc_name'];
			$teacher = $fetch['R_TEACHER'];
			$teacher1 = $fetch['R_TEACHER_1'];
			$teacher2 = $fetch['R_TEACHER_2'];
                
		?>
        	<tr>
                <td align="center"><?php echo $sno; ?>. </td>
                <td>
                    <h4><?php echo $title; ?><?php echo $name; ?>  <?php echo $lname; ?></h4>
                    <p><small><i class="fa fa-user"></i> <?php echo $skill; ?> <strong>ระดับ</strong> <?php echo $level; ?></small><br>
                    <small><i class="fa fa-mortar-board"></i> รหัส  <?php echo $school_id; ?><?php echo $std_id; ?>  <?php echo $school; ?></small></p>
                </td>
                <td>
                	<p>อ.<?php echo $teacher; ?></p>
					<p><?php if ($R_TEACHER_1){ ?>อ.<?php echo $teacher1; ?><?php } ?></p>
					<p><?php if ($R_TEACHER_2){ ?>อ.<?php echo $teacher2; ?><?php } ?></p>
                </td>
                <td><a href="?op=admin&a=student&edit=<?=$fetch['R_ID']?>" onClick="window.location" title="แก้ไข"><i class="fa fa-pencil-square-o"></i></a></td>
                <td><a href="?op=admin&a=student&del=<?=$fetch['R_ID']?>" onClick="return confirm('ยืนยันการลบข้อมูล?')"><i class="fa fa-times"></i></a></td>
            </tr>
        <?php $sno ++; } ?>  
        </tbody>
	</table>

	</div>
</div>
</div>