select option ใช้เงื่อนไข if ไม่ได้ มันจะต้องเขียนเช็คค่ายังไงคะ

<table width="100%" border="0"  align="center" cellpadding="3" cellspacing="1">
  <tr>
  <td width="518" style="font-size:16px; font-weight:bold;">รายชื่อผู้สมัครงานทั้งหมด</td>
  <td width="167" align="right">
 
 <!-- <form action="position_add.php" method="get" name="add">
<div align="center"><input name="" type="submit" value="add" style="cursor:pointer;" /></div>
</form>-->
  </td>
  </tr>
  <tr>
    <td style="font-size:16px; font-weight:bold;">&nbsp;</td>
    <td align="right">&nbsp;</td>
  </tr>
  <tr>
    <td style="font-size:16px; font-weight:bold;"><form name="frmSearch" method="get" action="<?php echo $_SERVER['SCRIPT_NAME'];?>" onSubmit="return validate();">
ค้นหาจาก ชื่อ-สกุล
      <input name="txtKeyword" size="30" type="text" id="txtKeyword" value="<?=$_GET["txtKeyword"];?>" >
      <input type="submit" name="imageField" id="imageField" value="ค้นหา"  />
    </form>
    
 <form method="get" action="<?php echo $objResult["positionID"];?>">
<select name="jumpMenu" id="jumpMenu" onChange="MM_jumpMenu('parent',this,0)">
<option name="jumpMenu" value="">----แสดงข้อมูลในฐานข้อมูล--------</option>
<?php
$strSQL ="SELECT * FROM position";
$objQuery = mysql_query($strSQL);
while($objResult = mysql_fetch_array($objQuery)){
?>
<option value="apply_all2.php?positionID=<?php echo $objResult["positionID"];?>"<?php if($_GET['jumpMenu'] == 'positionID'){echo "checked";}?>><?php echo $objResult["position_name"];?></option>
<?php
}
?>
</select>



</form>
    
    </td>
    <td align="right">&nbsp;</td>
  </tr>
</table>

<?php

if($_GET["txtKeyword"] != ""){
	$strSQL ="	SELECT * FROM application WHERE name LIKE '%".$_GET["txtKeyword"]."%' ";
}else if($_GET["txtKeyword"] == ""){
	$strSQL ="	SELECT * FROM application ";
}else if($_GET["jumpMenu"] == 'positionID'){
	$strSQL ="	SELECT * FROM application a LEFT JOIN position b ON (a.positionID=b.positionID) WHERE a.positionID = '".$_GET ["positionID"]."' ";
}else if($_GET["jumpMenu"] == ""){
	$strSQL ="	SELECT * FROM application ";
}


//$strSQL ="SELECT * from application a left join position b on a.positionID=b.positionID where a.positionID='".$_GET ["positionID"]."' ";
	
$objQuery = mysql_query($strSQL) or die ("Error Query [".$strSQL."]");
$objResult = mysql_fetch_array($objQuery);
$Num_Rows = mysql_num_rows($objQuery);

$Per_Page = 10;   // Per Page

$Page = $_GET["Page"];
if(!$_GET["Page"]){
	$Page=1;
}

$Prev_Page = $Page-1;
$Next_Page = $Page+1;

$Page_Start = (($Per_Page*$Page)-$Per_Page);
if($Num_Rows<=$Per_Page){
	$Num_Pages =1;
}else if(($Num_Rows % $Per_Page)==0){
	$Num_Pages =($Num_Rows/$Per_Page) ;
}else{
	$Num_Pages =($Num_Rows/$Per_Page)+1;
	$Num_Pages = (int)$Num_Pages;
}
/*
	Order By = Incorrect
	ORDER BY = Correct
*/
$strSQL .=" ORDER BY appID DESC LIMIT $Page_Start , $Per_Page ";
$objQuery  = mysql_query($strSQL) or die ("Error Query [".$strSQL."]");
?>

<table width="100%" border="0" class="tbshow" bgcolor="#ccc" align="center" cellpadding="5" cellspacing="1">
  <tr>
    <td width="50" class="tbshowtr"><div>ลำดับ</div></td>
    <td width="250" class="tbshowtr"><div>ชื่อ-สกุล</div></td>   
    <td width="250" class="tbshowtr"><div>ตำแหน่ง</div></td>
    <td width="150" class="tbshowtr"><div>วันที่สมัคร</div></td>
    <td width="100" class="tbshowtr"><div>ดูใบสมัคร</div></td>
    <td width="100" class="tbshowtr"><div>เอกสาร</div></td>
  </tr>
  
<?php
$i=1;
if($Page > 1){
	$i = ($Per_Page * ($Page-1)) + 1; 
}

while($objResult = mysql_fetch_array($objQuery)){
?>
<tr bgcolor="#fff">
<td><div align="center"><?php echo $i;?></div></td>
<td align="center"><?php echo $objResult["name"];?></td>
<td align="center"><?php echo $objResult["positionName"];?></td>
<td align="center"><?php echo $objResult["Creatdate"];?></td>
<td align="center"><a href="apply_detail.php?appID=<?php echo $objResult["appID"];?>"><img src="../../images/view_icon.png" border="0"></a></td>
<td align="center"><a href="../../file/<?php echo $objResult["resume"];?>"><img src="../../images/dl_icon.png" border="0"></a></td>
</tr>
<?php
$i++;
}
?>
</table>

<?php
// coding here...
?>