Decrement numeric item's value, stored on a specific server

# Memcached::decrementByKey

(PECL memcached >= 2.0.0)

Memcached::decrementByKey — Decrement numeric item's value, stored on a specific server

### 说明

public function Memcached::decrementByKey(
string `$server_key`,
string `$key`,
int `$offset` = 1,
int `$initial_value` = 0,
int `$expiry` = 0
): int|false

Memcached::decrementByKey() decrements a numeric item's value by the specified `offset`. If the item's value is not numeric, an error will result. If the operation would decrease the value below 0, the new value will be 0. Memcached::decrementByKey() will set the item to the `initial_value` parameter if the key doesn't exist.

### 参数

`server_key`

  本键名用于识别储存和读取值的服务器。没有将实际的键名散列到具体的项目，而是在决定与哪一个 memcached 服务器通信时将其散列为服务器键名。这使得关联的项目在单一的服务上被组合起来以提高多重操作的效率。

`key`

  The key of the item to decrement.

`offset`

  The amount by which to decrement the item's value.

`initial_value`

  The value to set the item to if it doesn't currently exist.

`expiry`

  The expiry time to set on the item.

### 返回值

Returns item's new value on success 或者在失败时返回 `false`.

### 参见

- Memcached::decrement() - 减小数值元素的值
- Memcached::increment() - 增加数值元素的值
- Memcached::incrementByKey() - Increment numeric item's value, stored on a specific server

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