class BaseModel    {        private $tableName;        private $fields=array();        function __construct()        {            $this->tableName=rtrim(get_class($this),'M');        }        function __get($n)        {            return($this->$n);        }        function __set($n, $value)        {            $this->$n = $value;            $this->fields[$n]=$value;        }        function Add()        {            $f='';            $f1='';            $arrKeys=array_keys($this->fields);            foreach($arrKeys as $row)            {                $f.=$row.',';                $f1.=':'.$row.',';            }            $f=rtrim($f,',');            $f1=rtrim($f1,',');            $sql='insert into '.$this->tableName.'('.$f.') values('.$f1.')';            //echo $sql;            global $dbh;            return $dbh->edit($sql,$this->fields);        }        function Update($sql_where,$params=array())        {            $f='';            $f1='';            $arrKeys=array_keys($this->fields);                    foreach($arrKeys as $row)            {                $f.=$row.'=:'.$row.',';            }            $f=rtrim($f,',');            $sql='update '.$this->tableName.' set '.$f.' where '.$sql_where;                        $arrKeys1=array_keys($params);            foreach($arrKeys1 as $row)            {                $this->fields[$row]=$params[$row];            }                        global $dbh;            return $dbh->Edit($sql,$this->fields);        }                function Delete($sql_where,$params=array())        {            $sql='delete from '.$this->tableName.' where '.$sql_where;            //echo $sql;                        global $dbh;            return $dbh->Edit($sql,$params);        }    }