shmop_open
shmop_open can create or open a shared memory block.
Parameters
- key
-
System's id for the shared memory block. Can be passed as a decimal or hex.
- mode
-
The flags that you can use:
"a" for access (sets SHM_RDONLY for shmat) use this flag when you need to open an existing shared memory segment for read only
"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
"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.
"n" create a new memory segment (sets IPC_CREATE|IPC_EXCL) use this flag when you want to create a new shared memory segment but if one already exists with the same flag, fail. This is useful for security purposes, using this you can prevent race condition exploits.
- permissions
-
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
- 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 will return a Shmop instance that you can use to access the shared memory segment you've created. false is returned on failure.
Changelog
| Version | Description |
| 8.0.0 | On success, this function returns an Shmop instance now; previously, a resource was returned. |