Returns the length of a hash, in number of items
取得HASH表的长度。
Parameters
key
Return value
LONG the number of items in a hash, FALSE if the key doesn't exist or isn't a hash.
Example
$redis->delete('h')
$redis->hSet('h', 'key1', 'hello');
$redis->hSet('h', 'key2', 'plop');
$redis->hLen('h'); /* returns 2 */
