PHP page process separation

Question

If some php page is running some long process such as sleep or while loop that makes it take a while till it loads, does it affect on other processes from the same page ?,
I noticed when i try to open the same page with different short process, it also takes so long to load and to be clear it doesn't load before the first one (long process) does,

is it true or something's wrong with my code and how to prevent it ?
i think it has something to do with cache, i don't wanna mess up though before getting a tip or an answer

Answer 1

PHP run in a single process, each time you access the page, it start the process, process, and finish. Each process won't affect the others.

Answer 2

I noticed when i try to open the same page with different short process, [...] it doesn't load before the first one (long process) does

The most common reasons:

• Your scripts use PHP sessions "as is", which use file locking. The file locking mechanism ensures only one script at a time can edit the session data of each user, but this does mean that provided two requests from the same user happen simultaneously, a second script will not start before the first has finished if they both rely on sessions (two different users have different session files though, so they can't collide)
• The browser automatically detects the page is taking long and delays subsequent requests intentionally in the background — I believe this is something Google Chrome does by default.

Both cases are relatively safe however, because the delay is only present in case the same user is trying to load several pages simultaneously which is not usual — different users will not see delays regardless how long the actual page takes to load.

More on the topic in this excellent SO answer .