php Mutex?

[Anon]

Does php have any type of mutex or semaphore. Or anything that will gurantee me mutual exclusion. What i am trying to do is create order numbers. But i want to protect against two users retrieving their order numbers at the same exact instance. The way im creating order numbers is the numerical
two digit (month)(day)(year)(hour)(minute)(seconds) so for instance june 25 11:30.24pm is 062501233024 . is it possible that two users could intitiate a order number at the exact same instance giving me two identical order numbers. If so thats why i would need the mutex . Or does php have something builting to protect against something like this.

Thanks.
Ira

[kparker]

If you're running on a unix server, you can use the shmem/semaphore module. I'm not aware of anything comparable for NT. However, if you're using some kind of dbms, you'd be better off just letting the dbms generate some kind of unique number--in fact you'll probably need this anyway.

[badman]

hi,
The best option would be to let the database do it for you.(i am assuming that you will store the order number in a dbms and this would be the primary key).

That is generate the order number in your script,store it in a table .

Everytime you need to add another order number just select the most recent one ,increment it and store the new one. This way you can ensure that no two order numbers are same.(this is for the situation mentioned in your question)

Alternatively, you can set the order number as primary key with auto increment option and set the default value(start value) to any number you want. Alongwith this you can also have a date time stamp field which will tell you when the order was recorded.

i hope this helps! cheers

[Anon]

Look at php.net, sec. LXXVI Semaphore and Shared Memory Functions.