## zRank, zRevRank ##### *Description* Returns the rank of a given member in the specified sorted set, starting at 0 for the item with the smallest score. zRevRank starts at 0 for the item with the *largest* score. 返回key對應的有序集合中member元素的索引值，元素按照score從低到高進行排列。rank值（或index）是從0開始的，這意味著具有最低score值的元素的rank值為0。使用ZREVRANK可以獲得從高到低排列的元素的rank（或index）。 ##### *Parameters* *key* *member* ##### *Return value* *Long*, the item's score. ##### *Example* ``` <pre class="calibre9">$redis->delete('z'); $redis->zAdd('key', 1, 'one'); $redis->zAdd('key', 2, 'two'); $redis->zRank('key', 'one'); /* 0 */ $redis->zRank('key', 'two'); /* 1 */ $redis->zRevRank('key', 'one'); /* 1 */ $redis->zRevRank('key', 'two'); /* 0 */ ``` ##