LoginCode werkt niet

<?php
				//LOGIN CLASS

Class Login{
	private $username;
	private $password;
	
	
	public function __construct($user,$pass){
		
		$this->username=$user;
		$this->password=$pass;
		
	}
	public function Check($table,$field_username,$field_password){
		//table= the table where all valid admin user logins are saved
		//$field_username= The field in the database where the username is saved
		//$field_password= the field in the database where the user password with md5 encryption is saved
		
		$qry="SELECT COUNT(*) as number FROM ".$table." WHERE ".$field_username."='".$username."'AND  ".$field_password."='".$password."'";
		echo($qry);
		//echo($username);
		//echo($password);
		$res=mysql_query($qry) or die(mysql_error());
		$number=mysql_result($res,0,0);
		echo($number);
	}
}
?>

<?php
				//LOGIN CLASS
 
Class Login{
	private $username;
	private $password;
 
 
	public function __construct($user,$pass){
 
		$this->username=$user;
		$this->password=$pass;
 
	}
	public function Check($table,$field_username,$field_password){
		//table= the table where all valid admin user logins are saved
		//$field_username= The field in the database where the username is saved
		//$field_password= the field in the database where the user password with md5 encryption is saved
 
		$qry="SELECT COUNT(*) as number FROM ".$table." WHERE ".$field_username."='".$username."'AND  ".$field_password."='".$password."'";
		echo($qry);
		//echo($username);
		//echo($password);
		$res=mysql_query($qry) or die(mysql_error());
		$number=mysql_result($res,0,0);
		echo($number);
	}
}
?>

<?php if(isset($_POST['cmdLogin'])){
	
		$login=new Login($_POST['txtGebruikersnaam'],$_POST['txtWachtwoord']);
		$mysql_connect=new Mysql_connect("localhost","root","mysql");
		$mysql_connect->mysql_db_connect("mailinglist");
		$login->Check("validlogins","username","password");
		$mysql_connect->mysql_disconnect();
	}
	 ?>

<?php if(isset($_POST['cmdLogin'])){
 
		$login=new Login($_POST['txtGebruikersnaam'],$_POST['txtWachtwoord']);
		$mysql_connect=new Mysql_connect("localhost","root","mysql");
		$mysql_connect->mysql_db_connect("mailinglist");
		$login->Check("validlogins","username","password");
		$mysql_connect->mysql_disconnect();
	}
	 ?>