sem_get

(PHP 4, PHP 5, PHP 7)

sem_getGet a semaphore id

Description

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().

Parameters

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.

Return Values

Returns a positive semaphore identifier on success, or false on error.

Changelog

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.

Notes

Warning

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

© 1997–2020 The PHP Documentation Group
Licensed under the Creative Commons Attribution License v3.0 or later.
https://www.php.net/manual/en/function.sem-get.php