PHP Manual: Release a semaphore

bool sem_release(SysvSemaphore $semaphore)

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.

Returns true on success or false on failure.

Version	Description
8.0.0	`semaphore` expects a SysvSemaphore instance now; previously, a resource was expected.

sem_release