Returns the rank of `member`

in the sorted set stored at `key`

, with the scores
ordered from low to high.
The rank (or index) is 0-based, which means that the member with the lowest
score has rank `0`

.

Use `ZREVRANK`

to get the rank of an element with the scores ordered from high
to low.

@return

- If
`member`

exists in the sorted set, @integer-reply: the rank of`member`

. - If
`member`

does not exist in the sorted set or`key`

does not exist, @bulk-string-reply:`nil`

.

@examples

```
ZADD myzset 1 "one"
ZADD myzset 2 "two"
ZADD myzset 3 "three"
ZRANK myzset "three"
ZRANK myzset "four"
```