这是我的JSON：

[
    {
        "id": "38",
        "article_id": "16",
        "news_event": "625",
        "language": "en",
        "channel_partner_id": "625",
        "title": "Test",
        "show_logo": null,
        "description": "test\n\n",
        "schedule": null,
        "event_date": "2012-03-09 10:08:35",
        "link_text": null,
        "guid": null,
        "timestamp": "2012-03-09 11:19:42",
        "website": null,
        "show_hours": null,
        "page_text": null
    },
    {
        "id": "37",
        "article_id": "15",
        "news_event": "625",
        "language": "en",
        "channel_partner_id": "625",
        "title": "Test",
        "show_logo": null,
        "description": "test\n\n",
        "schedule": null,
        "event_date": "2012-03-09 10:08:35",
        "link_text": null,
        "guid": null,
        "timestamp": "2012-03-09 11:19:39",
        "website": null,
        "show_hours": null,
        "page_text": null
    },
    {
        "id": "36",
        "article_id": "14",
        "news_event": "625",
        "language": "en",
        "channel_partner_id": "625",
        "title": "Test",
        "show_logo": null,
        "description": "test\n\n",
        "schedule": null,
        "event_date": "2012-03-09 10:08:35",
        "link_text": null,
        "guid": null,
        "timestamp": "2012-03-09 11:19:35",
        "website": null,
        "show_hours": null,
        "page_text": null
    },
    {
        "id": "35",
        "article_id": "13",
        "news_event": "625",
        "language": "en",
        "channel_partner_id": "625",
        "title": "Test",
        "show_logo": null,
        "description": "test\n\n",
        "schedule": null,
        "event_date": "2012-03-09 10:08:35",
        "link_text": null,
        "guid": null,
        "timestamp": "2012-03-09 11:19:31",
        "website": null,
        "show_hours": null,
        "page_text": null
    }
]

如何计算其中的对象数量？