# sem_release

(PHP 4, PHP 5, PHP 7)

sem_release — Release a semaphore

### 说明

sem_release ( resource `$sem_identifier` ) : bool

sem_release() releases the semaphore if it is currently acquired by the calling process, otherwise a warning is generated.

After releasing the semaphore, sem_acquire() may be called to re-acquire it.

### 参数

`sem_identifier`

  A Semaphore resource handle as returned by sem_get().

### 返回值

成功时返回 `TRUE`， 或者在失败时返回 `FALSE`。

### 参见

- sem_get() - Get a semaphore id
- sem_acquire() - Acquire a semaphore