Semaphore Functions
PHP Manual

sem_get

Get a semaphore id

Description

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.

Parameters

key

max_acquire

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

perm

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
4.3.0 The auto_release parameter was added.

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

  • sem_acquire
  • sem_release
  • ftok