将MySQL数据转换为JSON并包含MySQL计数

我有一个WordPress站点的自定义数据库表。我试图保存MySQL调用JSON的数据。该表包含一个日期列。我想计算一下每个日期出现的次数。然后我想保存日期和它在JSON对象中出现的次数。这是我的密码:

global $wpdb;
$table_name = $wpdb->prefix . "rlwpentries";

$query = $wpdb->get_results( "SELECT date, count(date) FROM $table_name group by date" );

$data = array();
foreach ($query as $row) {
$data[] = array('date' => $row->date, 'count' => $row->count);
}

print json_encode($data);

[  
    {  
        "date":"0000-00-00 00:00:00",
        "count":null
    },
    {  
        "date":"2019-02-22 00:00:00",
        "count":null
    },
    {  
        "date":"2019-02-23 00:00:00",
        "count":null
    },
    {  
        "date":"2019-02-24 00:00:00",
        "count":null
    },
    {  
        "date":"2019-02-25 08:00:00",
        "count":null
    },
    {  
        "date":"2019-02-26 00:00:00",
        "count":null
    }
]