shm_attach
shm_attach
(PHP 4, PHP 5, PHP 7)
shm_attach — Creates or open a shared memory segment
Description
resource shm_attach ( int $key [, int $memsize [, int $perm = 0666 ]] )
shm_attach() returns an id that can be used to access the System V shared memory with the given key, the first call creates the shared memory segment with memsize and the optional perm-bits perm.
A second call to shm_attach() for the same key will return a different shared memory identifier, but both identifiers access the same underlying shared memory. memsize and perm will be ignored.
Parameters
key
A numeric shared memory segment ID
memsize
The memory size. If not provided, default to the sysvshm.init_mem in the php.ini, otherwise 10000 bytes.
perm
The optional permission bits. Default to 0666.
Return Values
Returns a shared memory segment identifier.
Changelog
| Version | Description |
|---|---|
| 5.3.0 | This function now returns a resource instead of an integer. |
Notes
Note: This function used to return an integer value prior to PHP 5.3.0. To achieve the same value in a portable manner, the return value can be cast to an integer like: <?php // Create a temporary file and return its path $tmp = tempnam('/tmp', 'PHP' // Get the file token key $key = ftok($tmp, 'a' // Attach the SHM resource, notice the cast afterwards $id = shm\_attach($key if ($id === false) { die('Unable to create the shared memory segment' } // Cast to integer, since prior to PHP 5.3.0 the resource id // is returned which can be exposed when casting a resource // to an integer $id = (integer) $id; ?>
See Also
- shm_detach() - Disconnects from shared memory segment
- ftok() - Convert a pathname and a project identifier to a System V IPC key
← sem_remove
shm_detach →
© 1997–2017 The PHP Documentation Group
Licensed under the Creative Commons Attribution License v3.0 or later.
