[wp-hackers] Memory Space Changed Simultaneously

[Computer Guru]

What happens in PHP if a single address in memory attempts to be changed at
the very same exact time/cycle?

I have a problem with an auto-prepended file, it's the request_uri fix I
developed for WP users earlier, and it attempts to write to the global
$SERVER_[REQUEST_URI]

Since it's an auto-prepend file, the likelihood of simultaneous access is
very high, and under load I see this error:

Error using $this when it's not a context

Or something like that, and my code is very straightforward and simple, I
suspect this is what's happening.

May I'm not googling the right terms, but I can't find if
simultaneous-access crashes PHP or not. Does anyone know what happens when
there's a "race" to change the same memory address in PHP, and more
importantly, how to avoid it?

Computer Guru
NeoSmart Technologies
http://neosmart.net/blog/