shm_attach Creates or open a shared memory segment intshm_attach intkey intmemsize intperm shm_attach returns an id that 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 (default: sysvshm.init_mem in the &php.ini;, otherwise 10000 bytes) and the optional perm-bits perm (default: 0666). 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. See also ftok, and shm_detach.