PHPでJSON文字列を整形する方法です。

json_encode関数は、2番目の引数にJSON_PRETTY_PRINTを指定すると、返される結果の書式を、スペースを使って整えます。

参考

• PHP: json_encode – Manual
• PHP: 定義済み定数 – Manual

JSON文字列を用意します。

$json = '{"browsers": {"firefox": {"name": "Firefox","pref_url": "about:config","releases": {"1": {"release_date": "2004-11-09","status": "retired","engine": "Gecko","engine_version": "1.7"}}}}}';

JSON文字列をjson_decode関数でデコードし、json_encode関数でエンコードすると、整形された文字列を取得できます。

json_encode(json_decode($json), JSON_UNESCAPED_UNICODE | JSON_PRETTY_PRINT);

>>> $json = '{"browsers": {"firefox": {"name": "Firefox","pref_url": "about:config","releases": {"1": {"release_date": "2004-11-09","status": "retired","engine": "Gecko","engine_version": "1.7"}}}}}';
=> "{"browsers": {"firefox": {"name": "Firefox","pref_url": "about:config","releases": {"1": {"release_date": "2004-11-09","status": "retired","engine": "Gecko","engine_version": "1.7"}}}}}"
>>> json_encode(json_decode($json), JSON_UNESCAPED_UNICODE | JSON_PRETTY_PRINT);
=> """
   {\n
       "browsers": {\n
           "firefox": {\n
               "name": "Firefox",\n
               "pref_url": "about:config",\n
               "releases": {\n
                   "1": {\n
                       "release_date": "2004-11-09",\n
                       "status": "retired",\n
                       "engine": "Gecko",\n
                       "engine_version": "1.7"\n
                   }\n
               }\n
           }\n
       }\n
   }
   """
>>>