Since there aren't seperate functions for CREATING and ATTACHING shared memory (a mistake in my opinion), you might want to do some testing to check whether you've created it or not, as you may not want the slave of a master/slave pair to ever create the shared memory.
One way you can test this is by having your slave set the size to something small, then testing the size by putting a variable too large to fit, e.g.:
function get_shmem() {
return shm_attach(ftok('somefile.txt', 'T'), 100, 0644);
}
$shm = get_shmem();
while (!@shm_put_var($shm, 1, str_repeat('.....', 20))) {
shm_remove($shm);
sleep(1);
//we created it, so we'll remove it and sleep to wait for the master to create it, then try again.
$shm = get_shmem();
}
shm_remove_var($shm, 1);
//here we know the shared memory was already created, because we could put a variable in bigger than the size requested.
Another way you can handle it is to have all programs initialize the shared memory with the same parameters... I had a problem with this when my clients starting too fast and created the shmem without passing a memsize value, so it was defaulting to 10k which was too small.
