二维数组foreach改变二维字段值

数组
array(6) {   
 [0]=>   
 array(11) {   
   ["id"]=>   
   string(2) "76"   
   ["topic_id"]=>   
   string(1) "2"   
   ["title"]=>   
   string(48) "完善配套"   
   ["kwords"]=>   
   string(0) ""   
   ["description"]=>   
   string(48) "社区的完善配套"   
   ["content"]=>   
   string(55) "<p>粉红色风式碎发</p>"   
   ["pic"]=>   
   string(32) "./uploads/201411080511370202.png"   
   ["author"]=>   
   string(6) "系统"   
   ["uptime"]=>   
   string(19) "2014-11-08 17:25:37"   
   ["is_show"]=>   
   string(1) "1"   
   ["article_topic"]=>   
   array(4) {   
     ["id"]=>   
     string(1) "2"   
     ["name"]=>   
     string(12) "工程进度"   
     ["parent_id"]=>   
     string(1) "0"   
     ["is_show"]=>   
     string(1) "1"   
   }   
 }   
 [1]=>   
 array(11) {   
   ["id"]=>   
   string(2) "75"   
   ["topic_id"]=>   
   string(1) "2"   
   ["title"]=>   
   string(48) "干撒大哥"   
   ["kwords"]=>   
   string(0) ""   
   ["description"]=>   
   string(48) "啊哈哈个地方哈电话"   
   ["content"]=>   
   string(55) "<p>大啊等哈打嘎</p>"   
   ["pic"]=>   
   string(32) "./uploads/201411080511220202.png"   
   ["author"]=>   
   string(6) "SAAB系统"   
   ["uptime"]=>   
   string(19) "2014-11-08 17:25:22"   
   ["is_show"]=>   
   string(1) "1"   
   ["article_topic"]=>   
   array(4) {   
     ["id"]=>   
     string(1) "2"   
     ["name"]=>   
     string(12) "东方红进度"   
     ["parent_id"]=>   
     string(1) "0"   
     ["is_show"]=>   
     string(1) "1"   
   }   
 }   
.
.
.
}
//要把每个 ["uptime"]=>string(19) "2013-11-08 17:45:12"    里面的日期换成‘xxxx-xx-xx’格式

这样，已经确定了uptime这个键名在第二维是吧
使用

foreach ($array as &$arr){
    $arr['uptime'] = date('Y-m-d', strtotime($arr['uptime']));  //改变字段值
    $arr['new_color'] = "red";    //添加新的字段
}