Re: How php works?

Thanks Jochem, Roman :) On 12/13/06, Jochem Maas <jochem@iamjochem.com> wrote:

Kai Xiang wrote: On 12/13/06, Roman Neuhauser <neuhauser@sigpipe.cz> wrote:

# maillist.kai@gmail.com / 2006-12-13 14:15:26 +0800:

I'm new here and looking PHP these days, howerver , I'm confused by

how

it

works, and here is some questions I have. Is there any old bird wanna help me out? 1. I heard there is a zend engine inside PHP playing the role as a

virtual

machine, and PHP excution have 2 step, first compile to opcode and

then

excute the opcode, so is that means the php are compiled only once per file? or still

need

to

recompile when another request issued to the server? also I heard

about

the

caching extention about php, is it talking about caching the opcode?

is't

caching the opcode or excute results? how it shares between the

requests? Both kinds of things exist, with different sharing strategies.

Can you tell it more detail, opcode caching cache the compiled opcode, so not any compile needed anymore if no source changed? what about results, what kind of methdology it's taking? you can get a good idea of APC from the changelog:

       http://pecl.php.net/package-changelog.php?package=APC

Zend als offers opcode caching as part of their suite of products ... Im not all to familiar with Zend's stuff but no doubt their website has plenty of info.

3. Take linux apache for example, if compiled as a apache module, and

using

prefork threading model, for example, if I have 100 process, is that

means I

have 100 copy of PHP library local data(I assume only one reentrant excutable image) in each process? compare to a worker model, like 10

process

and 10 threads in each one process, should it make a difference that

we

only

have 10 copy of PHP library local data ?

Practical concerns make your question moot: even if the basic distribution was all threadsafe, you're bound to hit a library that

uses

strtok(3) or strerror(3), or static variables. How much of the code you rely on is labelled by its authors as threadsafe?

So it is not a good idea to use worker and php module at the same time, but correct - stick with the prefork module with apache, I believe *think* it is possible to safely use a threaded module if you decide to go the FastCGI route but I maybe thinking this because I completely misunderstood what someone was saying about FastCGI (I remember reading quite abit about FastCGI in posts made to internals@lists.php.net by core-dev/Zend-Founder Andi Gutmans - although I can't say I understood everything I read!) if no threadsafe problem , maybe my thinking is right? Btw, I thought strerror in libc were thread-safe.