PHP转换为JSON对象

我有一个关联数组，需要将其转换为非常特定的JSON字符串。当前我的阵列如下所示：

$arr = array(
    array(
        'data' => array(
            'a' => 1, 'b' => 2, 'c' => 3, 'd' => 4, 'e' => 5
        ),
        array(
            'a' => 1, 'b' => 2, 'c' => 3, 'd' => 4, 'e' => 5
        )
    )
);

{"data":[{"a":1,"b":2,"c":3,"d":4,"e":5},{"a":1,"b":2,"c":3,"d":4,"e":5}]}

{"data":[{"a":1,"b":2,"c":3,"d":4,"e":5},{"a":1,"b":2,"c":3,"d":4,"e":5}]}

此JSON编码为：

[{"data":{"a":1,"b":2,"c":3,"d":4,"e":5},"0":{"a":1,"b":2,"c":3,"d":4,"e":5}}]

我需要JSON如下所示：

$arr = array(
    array(
        'data' => array(
            'a' => 1, 'b' => 2, 'c' => 3, 'd' => 4, 'e' => 5
        ),
        array(
            'a' => 1, 'b' => 2, 'c' => 3, 'd' => 4, 'e' => 5
        )
    )
);

{"data":[{"a":1,"b":2,"c":3,"d":4,"e":5},{"a":1,"b":2,"c":3,"d":4,"e":5}]}

{"data":[{"a":1,"b":2,"c":3,"d":4,"e":5},{"a":1,"b":2,"c":3,"d":4,"e":5}]}

请记住，这是我的数组中的一个表示形式，它的大小可能会有所不同。目前它有两项记录，但很可能会有更多

如何对数组进行编码以符合我的要求？尝试以下方法：

$arr = array(
       'data' => array(
        0=>array('a' => 1, 'b' => 2, 'c' => 3, 'd' => 4, 'e' => 5),
        1=>array('a' => 1, 'b' => 2, 'c' => 3, 'd' => 4, 'e' => 5)
        )
);

对我来说，这产生了：