shm_attach

(PHP 4, PHP 5, PHP 7)

shm_attach — Creates or open a shared memory segment

Description

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

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 →

Licensed under the Creative Commons Attribution License v3.0 or later.

https://secure.php.net/manual/en/function.shm-attach.php