สอบถามการใช้ if else ตรวจเช็คค่า session ว่ามันตรงกับฐานข้อมูล แต่พอใช้ if else มันไม่วนเข้าลูปอะค่ะทั้งที่ข้อมูลตรงกัน

session_start();
$session=session_id();
  
header("Content-type:text/html; charset=UTF-8");          
header("Cache-Control: no-store, no-cache, must-revalidate");         
header("Cache-Control: post-check=0, pre-check=0", false);         


$connect2 = mysql_connect("localhost","muayhoo_hoo","pR^;aN*UK7s7","TRUE");
mysql_select_db('muayhoo_hoo',$connect2);
mysql_query("SET NAMES 'utf8'",$connect2);
mysql_query("SET character_set_results=utf8");
mysql_query("SET character_set_client='utf8' ");
mysql_query("SET character_set_connection='utf8' ");
mysql_query("collation_connection = utf8_unicode_ci");
mysql_query("collation_database = utf8_unicode_ci");
mysql_query("collation_server = utf8_unicode_ci");

$member="SELECT * FROM member_login WHERE username='".$_SESSION['username']."'";
$result_mem=mysql_query($member);
$show_mem=mysql_fetch_array($result_mem);
$session_db=$show_mem['session'];
			
			
	if($session_db=='$session') {
				
		echo "yes";		
		echo "<script language='javascript'>alert('Completed.');window.location='index.php?view=home';</script>";
			
	}else{
				
		echo "no";		
		echo "<script language=Javascript>window.location.href=\"index.php?view=home\";</script>";
	}