php oop method insert ใช้งานไม่ได้ครับ เพิ่งหัดเขียนนะครับ

<?php 
class db{
	
	var $dbhost="localhost";
	var $dbusername="root";
	var $dbpassword="1234";
	var $dbname="oop";
	var $connect_status;
	var $selectdb_status;
	var $insert_status;
		function connect(){
			
				$this->constatus=mysql_connect($this->dbhost,$this->dbusername,$this->dbpassword);
			
				if(!$this->connect_status){
				echo mysql_error();
				}else{
				
					$this->selectdb_status=mysql_select_db($this->dbname);
						if(!$this->selectdb_status){
					
						echo mysql_error();
					
					}
				}
			
			}
			
		function insert($tables_name,$field_name,$values){
		
		 $this->insert_status=mysql_query("insert into {$tables_name}(($field_name))values({$values})");
			if(!$this->insert_status){
			echo mysql_error();//ฟ้องตรงนี้ว่า  No database selected
			
			}

		}

	}

?>

<?php 
include"classdb.php";
$connect=new db();
$connect->connect();
$connect->insert("student","s_id,s_name","'1234567','สมปอง'");

?>