ขอคำแนะนำเกี่ยวการล็อกอินด้วยค่ะ ว่าทำไมเมื่อเพิ่มการทำลาย session ในไฟล์ล็อกเอาท์ พอมาล็อกอินใหม่ต้องล็อกอินสองครั้งถึงจะผ่าน

<?session_start();
include("nusoap/nusoap.php");
include ("connect_db.php");
$txtUsername=$_POST['txtUsername'];
$txtPassword=$_POST['txtPassword'];
$strSQL = "SELECT * FROM OFFICER WHERE USERNAME = '".trim($_POST['txtUsername'])."' and PASSWORD = '".trim($_POST['txtPassword'])."'";
$objParse = oci_parse ($objConnect, $strSQL);
oci_execute ($objParse,OCI_DEFAULT);
$objResult = oci_fetch_array($objParse,OCI_BOTH);
//$type_id=$row["type_id"];
   $OFFICERID=$objResult["OFFICERID"];
	if ($objResult)
{$_SESSION["OFFICERID"] = $objResult["OFFICERID"];
$_SESSION["OFFICERNAME"] = $objResult["OFFICERNAME"];
$_SESSION["OFFICERSURNAME"] = $objResult["OFFICERSURNAME"];
$_SESSION["type_id"] = $objResult["type_id"];
	if ($type_id== '1')
{
	echo "<meta http-equiv='refresh' content='50;URL=index1.php'>";	
	//header("location:index1.php");
	session_write_close(); //¨º¡ÒÃÊÃéÒ§ session //
	}
	else if ($type_id== "2")
		{
	echo "<meta http-equiv='refresh' content='50;URL=index_officer.php'>";	
      	//header("location:index_officer.php");
	session_write_close(); //¨º¡ÒÃÊÃéÒ§ session //
		}
	else if ($type_id== "3")
	{
	echo "<meta http-equiv='refresh' content='50;URL=index_officer1.php'>";	
    	//header("location:index_officer1.php");
	session_write_close(); //¨º¡ÒÃÊÃéÒ§ session //
				}
				
				
    }else{
	/*echo"<script language='JavaScript'>";
               echo"alert('ª×èÍáÅÐÃËÑʼèÒ¹äÁè¶Ù¡µéͧ');"; 
	echo"</script >";
	echo "<meta http-equiv='refresh' content='0;URL=login_admin.php'>";*/
					      }	
////////////////////////////////////////////////////////////////////////////////////////////////////////////////
$client = new nusoap_client('http://webservice.yru.ac.th/server/ns_getstudent.php?wsdl', true);
  $result= $client->call('auth', array('username' => $txtUsername,'password' => $txtPassword));
					
	if ($result<>"กรุณาตรวจสอบชื่อผู้ใช้และรหัสผ่าน")
	{
		$b = explode(",",$result); 
		$_SESSION["student_code"]= $b[0]; //????????????
		$_SESSION["cars_id"]=$b[1]; //???? ???.
		$_SESSION["prefix"]=$b[2]; //????????
		$_SESSION["std_name"]=$b[3];//????????????
		$_SESSION["std_surname"]=$b[4];//???????
		$_SESSION["program"]=$b[5];//????????
		$_SESSION["faculty"]=$b[6];//???
		session_write_close(); //?????????? session //
         echo "<meta http-equiv='refresh' content='50;URL=index_std.php?student_code=".$_SESSION["student_code"]."' >"; 
                        		                    			
	}else {
		echo"<script language='JavaScript'>";
	 echo"alert('ª×èÍáÅÐÃËÑʼèÒ¹äÁè¶Ù¡µéͧ');"; 
	echo"</script >";
	echo "<meta http-equiv='refresh' content='50;URL=login_admin.php'>";
	      //}
		  }
						 
	
?>

<?	session_start();
	include("nusoap/nusoap.php");
	include ("connect_db.php");
	$txtUsername=$_POST['txtUsername'];
	$txtPassword=$_POST['txtPassword'];
	$strSQL = "SELECT * FROM OFFICER WHERE USERNAME = '".trim($_POST['txtUsername'])."' and PASSWORD = '".trim($_POST['txtPassword'])."'";
	$objParse = oci_parse ($objConnect, $strSQL);
	oci_execute ($objParse);
	$objResult = oci_fetch_array($objParse,OCI_ASSOC);
	//$type_id=$row["type_id"];
   $OFFICERID=$objResult["OFFICERID"];
     oci_execute ($objParse);
	if (oci_fetch_all($objParse,$resultArr) >0 )
	{ $_SESSION["OFFICERID"] = $objResult["OFFICERID"];
	   $_SESSION["OFFICERNAME"] = $objResult["OFFICERNAME"];
	   $_SESSION["OFFICERSURNAME"] = $objResult["OFFICERSURNAME"];
	   $_SESSION["type_id"] = $objResult["type_id"];
	   if ($type_id== '1')
	   {
	     echo "<script>window.location='index1.php';</script>";	
	     
	      }
	      	else if ($type_id== "2")
	       {
		echo "<script>window.location='index_officer.php';</script>";	
		}
		else if ($type_id== "3")
		{
		echo "<script>window.location='index_officer1.php';</script>";	
		}
				
				
	    }else{
		/*echo"<script language='JavaScript'>";
		  echo"alert('ª×èÍáÅÐÃËÑʼèÒ¹äÁè¶Ù¡µéͧ');"; 
		echo"</script >";
		echo "<meta http-equiv='refresh' content='0;URL=login_admin.php'>";*/
					      }	
/////////////////////////////////////////////////////////////////////////////////////////////////////////////////
 	$client = new nusoap_client('http://webservice.yru.ac.th/server/ns_getstudent.php?wsdl', true);
	 $result= $client->call('auth', array('username' => $txtUsername,'password' => $txtPassword));
		
	if ($result<>"?????????????????????????????????")
	{
	$b = explode(",",$result); 
	$_SESSION["student_code"]= $b[0]; //????????????
	$_SESSION["cars_id"]=$b[1]; //???? ???.
	$_SESSION["prefix"]=$b[2]; //????????
	$_SESSION["std_name"]=$b[3];//????????????
	$_SESSION["std_surname"]=$b[4];//???????
	$_SESSION["program"]=$b[5];//????????
	$_SESSION["faculty"]=$b[6];//???
	//session_write_close(); //?????????? session //
 echo "<script>window.location='index_std.php?student_code=".$_SESSION["student_code"]."'</script>"; 
                      		                    			
	}else {
		echo"<script language='JavaScript'>";
			 echo"alert('ª×èÍáÅÐÃËÑʼèÒ¹äÁè¶Ù¡µéͧ');"; 			
			echo "<script>window.location='login_admin.php';</script>";

			      
				  }
 
?>

<?
session_start();
session_destroy();
?>
<html>
<head>
<title>ออกจากระบบ</title>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
</head>
<?
echo"<script language='JavaScript'>";
echo"alert('ออกจากระบบเรียบร้อย');"; 
echo "window.location='login_admin.php'; ";
echo "</script >";
exit(0);	
?>
</html>