"rec_items": [
        {
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            "gid": 6326585,
            "author": "我吃西紅柿",
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            "last_sort": 841,
            "last_chapter_name": "第二十五卷 第六章 一掃而空",
            "sub_count": 5364424,
            "novel_name": "莽荒紀",
            "last_update_time": 1393679718826
        },
        {
            "classes": "玄幻",
            "gid": 6109786,
            "author": "唐家三少",
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            "last_chapter_name": "第三百八十一章 開始行動（中）",
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            "novel_name": "絕世唐門",
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        },
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            "classes": "玄幻",
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            "author": "辰東",
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            "last_chapter_name": "第四百三十二章 扛媳婦回村",
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        },
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            "classes": "玄幻",
            "gid": 4711723,
            "author": "只是小蝦米",
            "nid": 12629406,
            "last_sort": 2603,
            "last_chapter_name": "第2588章 蘇醒！",
            "sub_count": 2841630,
            "novel_name": "武逆",
            "last_update_time": 1393605899300
        },
        {
            "classes": "玄幻",
            "gid": 3701669,
            "author": "蒼笑天",
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            "last_sort": 3427,
            "last_chapter_name": "第兩千兩百二十五章 孔雀王！",
            "sub_count": 606473,
            "novel_name": "武破九霄",
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        },
        {
            "classes": "玄幻",
            "gid": 8141499,
            "author": "風凌天下",
            "nid": 9212380,
            "last_sort": 2579,
            "last_chapter_name": "第五百二十六章 九劫、天帝之戰(zhàn)【七】",
            "sub_count": 3082857,
            "novel_name": "傲世九重天",
            "last_update_time": 1393677692614
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    ],
    "cate_book_items": [
        {
            "classes": "玄幻",
            "gid": 4711723,
            "author": "只是小蝦米",
            "nid": 12629406,
            "last_sort": 2603,
            "last_chapter_name": "第2588章 蘇醒！",
            "sub_count": 2841630,
            "novel_name": "武逆",
            "last_update_time": 1393605899300
        },
        {
            "classes": "玄幻",
            "gid": 3701669,
            "author": "蒼笑天",
            "nid": 8583556,
            "last_sort": 3427,
            "last_chapter_name": "第兩千兩百二十五章 孔雀王！",
            "sub_count": 606473,
            "novel_name": "武破九霄",
            "last_update_time": 1391279170831
        },
        {
            "classes": "玄幻",
            "gid": 10645516,
            "author": "辰東",
            "nid": 12649548,
            "last_sort": 478,
            "last_chapter_name": "第四百三十二章 扛媳婦回村",
            "sub_count": 1422482,
            "novel_name": "完美世界",
            "last_update_time": 1393681655610
        }
    ]
}';

function mult_unique($array)
{
  $return = array();
  foreach($array as $key=>$v)
  {
    if(!in_array($v, $return))
    {
      $return[$key]=$v;
    }
  }
  return $return;
}

$json = get_object_vars(json_decode($json));
$data = $json['rec_items'];
$data = array_merge_recursive($data, $json['cate_book_items']);

echo '<pre>';
print_r($data);
echo '<br>';
print_r(mult_unique($data));
echo '</pre>';
?>