Call to undefined function sem_get()

[#1]

Given the trouble I was having with sessions I thought I'd try to roll my own. But I need a semaphore to stop multiple http requests geting in each others way. However when I try this is get the above error.
Do I need to do something special to use semaphones be used in this hosting environment, or are they unavailable?
Peter

[#2]

This link may be of use to you.
http://www.php.net/manual/en/sem.installation.php

[#3]

Thanks Mook. Is compiling PHP something we can do from within the plusnet hosting environment? I assumed it was a shared environment and we couldn't do stuff like that.
Peter

[#4]

TBH I am not the person to ask, but I seriously doubt it, but you never know. But I am sure others will clarify but you may need to wait until morning till a member of the PN staff is available.

[#5]

A single PHP binary is provided by Hostopia to be shared by all users of the Plusnet cgi cluster. We aren't able to compile our own.
As far as I can tell semaphore support has not been compiled into our copy so associated functions will not be available.
David