Bing每日一图

    $time = date("Ymd", time());
    $log = "./log/" . $time . '.txt';
    //判断缓存文件是否存在
    if (file_exists($log)) {
        //读取缓存
        $imgurl = file_get_contents($log);
        //跳转至图片地址
        header("Location: $imgurl");
    } else {
        //获取bing背景图
        $str = file_get_contents('http://cn.bing.com/HPImageArchive.aspx?format=js&idx=0&n=1');
        //解析Bing官方接口Json
        $data = json_decode($str,true);
        //七牛CDN镜像加速
        $imgurl = 'http://s.cn.bing.net'.$data['images'][0]['urlbase']. '_1920x1080.jpg';
        //写入TXT用作缓存
        file_put_contents($log, $imgurl);
        //跳转至图片地址
        header("Location: $imgurl");
    }