PHP insight

[sneskid]

I've been needing some insight as to how PHP scripts are handled after they are "compiled" and so forth.
Here is a prolonged scenario... mostly how I understand PHP to currently work, or I should say the code behind the scenes that makes PHP work.

terms:
Let Access(name.php) mean someone from the web has accessed the file in the brackets
Let [#] represent an instance of the script
Let Finish[#] mean the script finaly finished running
Let Update(name.php) mean that script was changed somehow

Let - represent a statement to describe the scenario
Let * represent an action
Let ? represent a question I have

== The Scenario ==

- We just uploaded a PHP file called "snes.php"

*Access(snes.php) [1]
- This is the first time snes.php is accessed, so it will get compiled by the zend engine, then it should be in memory.
*Finish[1]

*Access(snes.php) [2]
- This time snes.php is already in memory, so it starts to do what it has to do quicker.

? Is Zend informed when a file is updated or does it check the file every time someone accesses it

- Due to requests user [2] made, snes.php will run a loop that may take a few seconds to complete.

*Update(snes.php)
- I make snes.php include another file called "kid.php"

*Access(snes.php) [3]
- The zend engine recognizes snes.php was altered, so it recompiles it.
- The zend engine also compiles kid.php because it is included by snes.php.
- a few seconds pass

? What happens to instance [2] that ran during this time? would it just live out it's course? or is the process somehow interrupted.

*Finish[2]
*Finish[3]

*Access(snes.php) [4]
- user[4] has made some requests that make snes.php run for a few seconds.
* Update(kid.php)
- We made snes.php smart, so it knows if kid.php has been updated, and it can decide to re-include kid.php
? is "re-including" even possible?
? what happens to class objects that already existed and became available from an older include
? will PHP recompile kid.php again for instance [4] of snes.php, or just use what's in memory from before

*Finish[4]



== Thanks ==