php怎么遍历以下json数组？

已知json数组格式如下

{
    "id":["1123","1377"],
    "uid":["24542","84358"],
    "sid":["37683","99089"],
    "pid":["44354","1900"],
    "gid":["5565","7280"],
    "oid":["34166","7890987"]
    }

用foreach循环方法怎么返回都是空的，还是说方法不对？我需要遍历[ ]里的值

foreach key value 即可，代码如下：

<?php

$json = '{
    "id":["1123","1377"],
    "uid":["24542","84358"],
    "sid":["37683","99089"],
    "pid":["44354","1900"],
    "gid":["5565","7280"],
    "oid":["34166","7890987"]
    }';

$json = json_decode($json,true);

foreach($json as $key=>$value){
    echo "$key  第一个： $value[0] 第二个： $value[1]\n";
}

遍历如下:

<?php
 $j = '{
    "id":["1123","1377"],
    "uid":["24542","84358"],
    "sid":["37683","99089"],
    "pid":["44354","1900"],
    "gid":["5565","7280"],
    "oid":["34166","7890987"]
    }';

foreach(json_decode($j) as $k=>$v){
    echo "$k \n";
    foreach($v as $a){
        echo "$a \n";
    }
}


/*
打印结果:

id 
1123 
1377 
uid 
24542 
84358 
sid 
37683 
99089 
pid 
44354 
1900 
gid 
5565 
7280 
oid 
34166 
7890987 
*/

?>