Debug en netbeans con php, no continua siclo

<?php class DB_Personas { private static $_driver = DRIVER; private static $_port = PORT; private static $_server = SERVER; private static $_dbname = DBNAME; private static $_user = USER; private static $_passwd = PASSWD; private static $_connect;

// private function DB_Personas(){}

public static function Connection(){ //este seria el mètodo getInstance, el que permite la conexiòn a la base de datos
    $dsn= self::$_driver.":host=".self::$_server.":".self::$_port.";dbname=".self::$_dbname;
    if(!isset(self::$_connect)){
        self::$_connect=new PDO($dsn,self::$_user,self::$_passwd, [PDO::ATTR_PERSISTENT=>TRUE]);
        self::$_connect->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    }
    return self::$_connect;
 
}
public function Exec($sql){
    return self::$_connect->exec($sql);
}           
public function Query($sql){
    return self::$_connect->query($sql);
}
 
public function _clone(){
    trigger_error('Este objeto no se puede clonar', E_USER_ERROR);
 
}

}

?>