PHP performance question

I have a single PHP process (a WordPress plugin) that goes off to a number of other sites, waits for them to return information, and aggregates that information into a post. This process runs under a cron and takes quite a while to complete (all told, it can take 15 minutes to run).

I'm not concerned it takes so long to run, it's a big routine. What I am curious about, though, is whether page requests made to WordPress will be fed to users. I'm running this on a dedicated machine with a measurable amount of memory and processor resource and I have yet to field and test the system.

So, how well does PHP run when a long script is operating? Can it handle regular Web serving requests while there's one long script running?