Redis::hmGet()返回只有数值索引的数组

$redis->del('h');
$redis->hSet('h', 'field1', 'value1');
$redis->hSet('h', 'field2', 'value2');
$redis->hMGet('h', ['field1', 'field2', 'field3']理想状态下输出应该是

array (
 'field1' => 'value1',
 'field2' => 'value2',
 'field3' => null
)

但实际却是
array (
 0 => 'value1',
 1 => 'value2',
 2 => null
)