PHP ติดปัญหาทำระบบ Counter นับจำนวนผู้เข้าชม

 <?php
					$sql="select * from it_news where it_id='".$_GET[show]."';";
   					$dbquery = mysql_db_query($dbname, $sql);
    				$r=mysql_fetch_array($dbquery);
					$it_id=$r["it_id"];
					$titlenews=$r["title"];
					$story=$r["story"];
					$file_pic=$r["file_pic"];
					$date_time=$r["date_time"];
					/* ทำการ Update Counter โดย+1 */
					$counter=$r["counter"];
					echo $counter;
					$counter_new=$counter+1;
					**** $sql2="UPDATE it_news set $counter='$counter_new'";
					$dbquery2=mysql_db_query($db,$sql2);
					echo $sql2;
			?>