classe sul database

[techno]

Salve ho creato una classe per connettermi e chiudere un database:

class mysqlclass
{
    
    private $host="localhost";
    private $user="root";
    private $password="";
    
    public function connect(){
        
        $database="network";
        $dbconn=mysql_connect($this->host,$this->user,$this->password);
        mysql_select_db($database,$dbconn);
        
    }
    
    public function disconnect(){
        
        global $dbconn;
        mysql_close($dbconn);
    }
    
} 

ma mi da questo errore:
Warning: mysql_close(): supplied argument is not a valid MySQL-Link resource