(PHP 4, PHP 5, PHP 7, PHP 8)
sem_get — Get a semaphore id
$key
, int $max_acquire = 1
, int $permissions = 0666
, bool $auto_release = true
) : SysvSemaphore|false
sem_get() returns an id that can be used to
access the System V semaphore with the given key.
A second call to sem_get() for the same key will return a different semaphore identifier, but both identifiers access the same underlying semaphore.
If key is 0, a new private semaphore
is created for each call to sem_get().
key
max_acquire
The number of processes that can acquire the semaphore simultaneously
is set to max_acquire.
permissionsThe semaphore permissions. Actually this value is set only if the process finds it is the only process currently attached to the semaphore.
auto_releaseSpecifies if the semaphore should be automatically released on request shutdown.
Returns a positive semaphore identifier on success, or false on
error.
| 版本 | 说明 |
|---|---|
| 8.0.0 | On success, this function returns a SysvSemaphore instance now; previously, a resource was returned. |
| 8.0.0 |
The type of auto_release has been changed from
int to bool.
|
When using sem_get() to access a semaphore created
outside PHP, note that the semaphore must have been created as a set of 3
semaphores (for example, by specifying 3 as the nsems
parameter when calling the C semget() function),
otherwise PHP will be unable to access the semaphore.