decr, decrBy
Description
Decrement the number stored at key by one. If the second argument is filled, it will be used as the integer value of the decrement.
对指定的KEY的值自减1。如何填写了第二个参数，将把第二个参数自减给KEY的值。Parameters
key
value: value that will be substracted to key (only for decrBy)
Return value
INT the new value
Examples
$redis->decr('key1'); /* key1 didn't exists, set to 0 before the increment */
/* and now has the value -1 */
$redis->decr('key1'); /* -2 */
$redis->decr('key1'); /* -3 */
$redis->decrBy('key1', 10); /* -13 */