Record user gender using redis bit operations

Reading and seeing content related to redis bit operations, there is an example in the book: For example, each user on the website has an auto-incremented ID, and a string type key is used to record the user's gender..., I want to know the specific operation of this recording method, or what the idea is. I know that it must be distinguished by bits 1 and 0, but how is it recorded?

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Reading and seeing content related to redis bit operations, there is an example in the book: For example, each user on the website has an auto-incremented ID, and a string type key is used to record the user's gender..., I want to know the specific operation of this recording method, or what the idea is. I know that it must be distinguished by bits 1 and 0, but how is it recorded?

setbit key offset, where offset is replaced by userid, if the user with ID 1 is male, just setbit key 1 1, if it is female, just setbit key 1 0, to get the gender of ID 1, just getbit key 1

<code class="php">$redis->mSet($userId,['age'=>18, 'gender'=>0]);//小明
$redis->mSet($userId2,['age'=>16, 'gender'=>1]);//小红

$user = $redis->mGet($userId);
echo $user['gender'];//
</code>