SHM_HAS_VAR(3) 1 SHM_HAS_VAR(3)shm_has_var - Check whether a specific entry existsSYNOPSIS
bool shm_has_var (resource $shm_identifier, int $variable_key)
DESCRIPTION
Checks whether a specific key exists inside a shared memory segment.
PARAMETERS
o $shm_identifier
- Shared memory segment, obtained from shm_attach(3).
o $variable_key
- The variable key.
RETURN VALUES
Returns TRUE if the entry exists, otherwise FALSE
SEE ALSO shm_get_var(3), shm_put_var(3).
PHP Documentation Group SHM_HAS_VAR(3)
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SHMOP_OPEN(3) 1 SHMOP_OPEN(3)shmop_open - Create or open shared memory blockSYNOPSIS
int shmop_open (int $key, string $flags, int $mode, int $size)
DESCRIPTION shmop_open(3) can create or open a shared memory block.
PARAMETERS
o $key
- System's id for the shared memory block. Can be passed as a decimal or hex.
o $flags
- The flags that you can use:
o "a" for access (sets SHM_RDONLY for shmat) use this flag when you need to open an existing shared memory segment for read
only
o "c" for create (sets IPC_CREATE) use this flag when you need to create a new shared memory segment or if a segment with the
same key exists, try to open it for read and write
o "w" for read & write access use this flag when you need to read and write to a shared memory segment, use this flag in most
cases.
o "n" create a new memory segment (sets IPC_CREATE|IPC_EXCL) use this flag when you want to create a new shared memory seg-
ment but if one already exists with the same flag, fail. This is useful for security purposes, using this you can prevent
race condition exploits.
o $mode
- The permissions that you wish to assign to your memory segment, those are the same as permission for a file. Permissions need to
be passed in octal form, like for example 0644
o $size
- The size of the shared memory block you wish to create in bytes
Note
Note: the 3rd and 4th should be entered as 0 if you are opening an existing memory segment.
RETURN VALUES
On success shmop_open(3) will return an id that you can use to access the shared memory segment you've created. FALSE is returned on
failure.
EXAMPLES
Example #1
Create a new shared memory block
<?php
$shm_key = ftok(__FILE__, 't');
$shm_id = shmop_open($shm_key, "c", 0644, 100);
?>
This example opened a shared memory block with a system id returned by ftok(3).
SEE ALSO shmop_close(3), shmop_delete(3).
PHP Documentation Group SHMOP_OPEN(3)
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