从MySQL缓存文件中导出列值

I have one problem here. I'm using file as cache for storing MySQL result. Here are the results inside the cache file:

[
   {
      "Name":"Bell",
      "Class":"BWB0",
      "Lv":31,
      "Kill":0,
      "Serial":3,
      "PvpPoint":0,
      "Death":0
   },
   {
      "Name":"Perkss",
      "Class":"AWB0",
      "Lv":17,
      "Kill":0,
      "Serial":6,
      "PvpPoint":2400,
      "Death":0
   },
   {
      "Name":"1233",
      "Class":"BWB0",
      "Lv":3,
      "Kill":0,
      "Serial":1,
      "PvpPoint":0,
      "Death":0
   },
   {
      "Name":"Cora",
      "Class":"CWB0",
      "Lv":1,
      "Kill":0,
      "Serial":4,
      "PvpPoint":0,
      "Death":0
   }
]

Any idea to convert the result cache file into usual output ? like "echo $row['Name']".

Thanks, I'm just a newbie want to learn PHP :)

$json_string = '[{"Name":"Bell","Class":"BWB0","Lv":31,"Kill":0,"Serial":3,"PvpPoint":0,"Death":0},{"Name":"Perkss","Class":"AWB0","Lv":17,"Kill":0,"Serial":6,"PvpPoint":2400,"Death":0},{"Name":"1233","Class":"BWB0","Lv":3,"Kill":0,"Serial":1,"PvpPoint":0,"Death":0},{"Name":"Cora","Class":"CWB0","Lv":1,"Kill":0,"Serial":4,"PvpPoint":0,"Death":0}]';
$a = json_decode($json_string, true);

foreach($a as $row)
    {
    echo $row['Name'];
    }