On 12/13/06, Jochem Maas <jochem@[...].com>  wrote:
> 
>  Kai Xiang wrote:
>  > Hello all:
>  >
>  > 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?
> 
>  there are opcode caching mechanisms available (e.g. php.net/apc - which
>  needs to
>  be installed via 'pecl'**); however the standard php installation will not
>  do any
>  opcode caching (i.e. compilation to opcode is done at each request).
> 
>  ** pecl.php.net / pear.php.net


That sounds good, I can take a more look at it


>  >
>  > 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?
> 
>  no, there is no plugin replacement for the zend engine and AFAIK the zend
>  engine
>  is not used in any other products apart from php ... maybe zend.com has an
>  article on what exactly the zend engine is (I have never really bothered
>  to
>  find out myself :-).



> 
>  > 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 ?
> 
>  php is not threadsafe (well actually some php extensions are not thread
>  safe ...
>  it's an unknown quantity) the prefork worker module for apache2 is the
>  only
>  recommended way to go (if running as an apache module)
> 
>  you might want to look into the FastCGI SAPI if you need a speed boost ...
>  I can't tell you anything about it because I have no experience with it as
>  such.
> 
>  >
>  > 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 the place - always best to ask here first; if what your asking is
>  better aimed at the developers list someone here will point you in the
>  right direction.


That's fine, thanks


>  Thanks in advantage
>  >
>  > Regards
>  > Kai
>  >
> 
>