... PHP 4 >= 4.0.4) shmop_open -- Create or open shared memory block . int shmop_open ( int key, string flags, int mode, int size) . ... 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 . ... Create a new shared memory block . ...