Hi, I have this error Warning: mysql_num_rows() expects parameter 1 to be resource, boolean given in C:\Program Files\xampp\htdocs\nsubackend\lib\model\classLabType.php on line 9 & same in line 52.

here's my code:

function __construct($id=0){
		$con = new connection();
		$query = "SELECT * FROM tbllabtype WHERE labtypeID='".$id."'";
		$res = mysql_query($query);
		if(mysql_num_rows($res)>0){
			$row = mysql_fetch_array($res);
			$this->setLabTypeID($row['labtypeID']);
			$this->setLabTypeCode($row['labtypeCode']);
			$this->setLabTypeDesc($row['labtypeDesc']);
		}
		
	}
function showAllLabType(){
		$con = new connection();
		$query = "SELECT labtypeID FROM tbllabtype";
		$res = mysql_query($query);
		if(mysql_num_rows($res)>0){
			while($row = mysql_fetch_array($res)){
				$theid[] = $row['labtypeID'];
			}
			return $theid;
		}
		
	}

please, can somebody help me? thank you