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PHP Manual :: sem_get

sem_acquire || sem_release || Semaphore Functions || PHP Manual

(PHP 4, PHP 5, PHP 7)

sem_getGet a semaphore id


resource sem_get ( int $key [, int $max_acquire = 1 [, int $perm = 0666 [, int $auto_release = 1 ]]] )

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.




The number of processes that can acquire the semaphore simultaneously is set to max_acquire.


The semaphore permissions. Actually this value is set only if the process finds it is the only process currently attached to the semaphore.


Specifies if the semaphore should be automatically released on request shutdown.

Return Values

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.

See Also

sem_acquire || sem_release || Semaphore Functions || PHP Manual
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