Re: [PHP] How php works?

On Wed, December 13, 2006 12:15 am, Kai Xiang wrote:
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?

There is a Zend Engine inside the guts of PHP, and it does compile to
opcode and execute.

You can buy or find "opcode cache" software that will cache the
compiled opcode and run that on the next request.

Note that the BIG win there is not the compilation, but the hard drive
not getting hit to load in the PHP script.

2. Is there some alternative choise except zend engineen, why need a
zend
engine? for performance advantage or just easy for porting to
different
platform?

The original PHP guts were a hand-crafted parser by Rasmus Lerdorf,
who, and this is NOT meant to be pejorative, had no idea what he was
doing :-)
He didn't know that there were tools out there to write new computer
languages, and didn't use them.
So his parser was, well, kinda buggy, actually.
Ze'ev and Andi gutted the system with a shiny new parser using the pro
tools for homework, and ended up being Core PHP Developers by
accident. :-)
So, that became the Zend Engine, as Ze'ev and Andi's idea of a Good
Time is not building PHP websites, but building cool tools to improve
the guts of PHP, which is also why they started Zend (http://zend.com)
to sell high-end tools to high-end customers, like the Zend Cache.

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 ?

Yes, but if you don't use prefork, you have some serious thread safety
Risks, particularly in the extensions, and most especially in any
extensions that aren't getting heavy use already by people trying to
push into the threaded environment...

Stick with pre-fork unless your testing budget is 10 X your dev budget.

I'm not sure if this is the right place to talk about this, anyway, if
you
know a better place, help me out :)

This is probably about as on-topic a post as one can get, though much
of the info is "out there" if you can sift through the junk to find
it.

--
Some people have a "gift" link here.
Know what I want?
I want you to buy a CD from some starving artist.
http://cdbaby.com/browse/from/lynch
Yeah, I get a buck. So?
.

Relevant Pages

  • Re: [PHP] How php works?
    ... The most time consuming work in PHP isn't in PHP at all. ... compiling the code to opcode takes longer ... Because if you just did the file cache, it would be an equal amount of ... You could, in theory, take PHP, rip out its guts (aka the Zend Engine) ...
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  • Re: [PHP] How php works?
    ... >>> I'm new here and looking PHP these days, howerver, I'm confused by ... >>> excute the opcode, ... >>> caching extention about php, is it talking about caching the opcode? ... >> rely on is labelled by its authors as threadsafe? ...
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  • Re: [PHP] How php works?
    ... The most time consuming work in PHP isn't in PHP at all. ... compiling the code to opcode takes longer ... Because if you just did the file cache, it would be an equal amount of ... You could, in theory, take PHP, rip out its guts (aka the Zend Engine) ...
    (php.general)
  • How php works?
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    (php.general)
  • Re: [PHP] How php works?
    ... > I'm new here and looking PHP these days, howerver, I'm confused by how ... > machine, and PHP excution have 2 step, first compile to opcode and then ... > caching extention about php, is it talking about caching the opcode? ... distribution was all threadsafe, you're bound to hit a library that uses ...
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