(PHP 4, PHP 5, PHP 7)
sem_get — Get a semaphore id
sem_get ( int $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.
permissions
The semaphore permissions. Actually this value is set only if the process finds it is the only process currently attached to the semaphore.
auto_release
Specifies if the semaphore should be automatically released on request shutdown.
Returns a positive semaphore identifier on success, or false on error.
| Version | Description |
|---|---|
| 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.
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https://www.php.net/manual/en/function.sem-get.php