joomla pass logic

var $table='jos_users';
/*
Work on joomla 1.5
*/
public function detail($id,$field='username'){
        $sql=sprintf('select * from %s where %s="%s"',
          $this->table, $field, $id);
        return $this->resOne($sql ); //array (name,username,pass ...
    }

public function checkUser($username,$password){
        $data=$this->detail($username);
        $pass=$data['password'];
        $ar=explode(":",$pass);
        $pass2=md5($password.$ar[1]).":".$ar[1] ;
        $sql=sprintf("select count(id) c from %s where username='%s' and password='%s' and block=0",
        $this->table, $username,$pass2);
        $data=$this->resOne($sql,1);//array(c=>
        return $data['c']==1?true:false;
}