PHP嵌套循环输出导航[不使用递归]

where('parent_id=0')->select();		//$rs=$select->where('parent_id='.$parentid)->select();		for($i=0;$i'.$rs[$i]['index'].'';				$index=$rs[$i]['index'];			}			//去重输出首字母			if($rs[$i]['index']!=$index){				echo '
'.$rs[$i]['index'].'
';				$index=$rs[$i]['index'];			}			echo $rs[$i]['name'].'
';			$series=$select->where('parent_id='.$rs[$i]['id'])->select();			for($j=0;$j';				$model=$select->where('parent_id='.$series[$i]['id'])->select();				for($x=0;$x';				}				//for()			}		}    }}