(PHP 4, PHP 5, PHP 7)
shm_attach — Creates or open a shared memory segment
$key
[, int $memsize
[, int $perm = 0666
]] ) : resource
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.
keyA numeric shared memory segment ID
memsizeThe memory size. If not provided, default to the sysvshm.init_mem in the php.ini, otherwise 10000 bytes.
permThe optional permission bits. Default to 0666.
Returns a shared memory segment identifier.
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;
?>