Summary: Create or open shared memory block
resource shmop_open(int $key, string $flags, int $mode, int $size)
shmop_open() can create or open a shared memory block.
On success shmop_open() will return an resource that you can use to access the shared memory segment you've created.
FALSE is returned on failure.
- int $key: System's id for the shared memory block. Can be passed as a decimal or hex.
- string $flags: 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.
- int $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
- int $size: The size of the shared memory block you wish to create in bytes
Example #1 Create a new shared memory block
$shm_key = ftok(__FILE__, 't');
$shm_id = shmop_open($shm_key, "c", 0644, 100);
- Note: the 3rd and 4th should be entered as 0 if you are opening an existing memory segment.
|7.0.0||The return type of shmop_open() has been changed from int to resource.|