Shared Memory / Semaphores

Anon

Simple problem:
Write a chat. Don't write files, don't access a Database. It is possible. Perhaps with Shared Memory or Semaphores, but I just didn't get anything useful from these. Cookies would be a dumb idea, cause I want to write something into memory and have it read by another person. And not using a file or a database. For anyone who works on ASP as well, I'm talking about an application variable equivalent. I'm sure it works with Shared Memory, but I was not able to put an array in there (not even a serialized one).

Perhaps a simple example of how to use Shared Memory in PHP4 would help me a lot.

Cu,
Korkman

Anon

I am trying to do something with shared memory as well. I'm new to PHP, so I'm unsure of what it's capabilities are. Have you come across anything thus far?

Thanks for any advice,

Dean

Anon

Yeah, it's cool so far. I've built up a chat system with Shm/Sem. It goes like this:

Lock memory so no collisions occur (funny effects in a chat)

$shm_addr must be diffrent for every Script willing to use a diffrent memory

$shm_addr = 1;
$sem_id = sem_get($shm_addr);
sem_acquire($sem_id);

That about semaphores

Now to the real shared mem:

$shmid = shm_attach($shm_addr, $shm_size);
$alldata = shm_get_var($shmid, 1);
shm_detach($shmid);

There you got a var "$alldata" out of shm

Same procedure for writing

$shmid = shm_attach($shm_addr, $shm_size);
shm_put_var($shmid, 1, $alldata);
shm_detach($shmid);

After reading and writing, release the semaphore so the memory is shared

sem_release($sem_id);

So far it works really good. We had about 30 users in one chatroom and nothing went wrong. Really cool.

Dean wrote:

I am trying to do something with shared memory as well. I'm new to PHP, so I'm unsure of what it's capabilities are. Have you come across anything thus far?

Thanks for any advice,

Dean

bigby2k

I tried to do this code myself to see how it worked. You didn't seem to generate a value form $shm_size, or is that a system variable? Also, I got an error for shm_get_var that stated that the variable key 1 didn't exist.

Could you repost your code? I think you may have omitted a line or two.

Thanks,
Brian