think php sql () or ()

$map=array();
$condition=array();
     $condition['zt'] = 0;
          $condition['date'] = array('lt', $nowtime);;
          $condition['_logic'] = "and";
          $map['zt']=1;
          $map['date_hk']=array('lt', $nowtime);
          $map['_complex']=$condition;

          $map['_logic']='or';

where($map)