(PHP 4, PHP 5, PHP 7)
sem_get — Get a semaphore id
$key
[, int $max_acquire = 1
[, int $perm = 0666
[, int $auto_release = 1
]]] ) : resource
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.
key
max_acquire
The number of processes that can acquire the semaphore simultaneously
is set to max_acquire.
permThe 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.
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.