Re: [users@httpd] filters and handlers?

[Joshua Slive <jo...@slive.ca>]

On 8/19/07, Per Jessen <pe...@computer.org> wrote:
> I've been re-reading the manual to try to gain a better understanding of
> filters and handlers, specifically the difference between the two.
>
> The reason being -
>
> by default, the PHP interpreter is called as a handler (a typical
> config: "AddHandler application/x-httpd-php .phtml".  By implementation
> INCLUDES is a filter which is enabled using e.g.
> "AddOutputFilter INCLUDES shtml".
>
> I'd like to have my files processed first by the INCLUDES filter, then
> by the PHP handler.  The "AddOutputFilter" option clearly supports this
> type of sequence.
>
> But back to my initial question - what is the functional difference
> between a handler and a filter?

Handlers must originate the content themselves, whereas filters can
deal with content passed down from someplace else.

PHP is only a handler, due to zend's requirement that it deal with the
php file on disk and not in memory. (This was the argument at the
time, anyway. I'm not sure if things in php land have evolved since
that decision was made.) Therefore PHP must originate the content and
can't act on content passed from someplace else like mod_include.

Joshua.

---------------------------------------------------------------------
The official User-To-User support forum of the Apache HTTP Server Project.
See <URL:http://httpd.apache.org/userslist.html> for more info.
To unsubscribe, e-mail: users-unsubscribe@httpd.apache.org
   "   from the digest: users-digest-unsubscribe@httpd.apache.org
For additional commands, e-mail: users-help@httpd.apache.org

Re: [users@httpd] filters and handlers?

["William A. Rowe, Jr." <wr...@rowe-clan.net>]

Joshua Slive wrote:
> On 8/19/07, Per Jessen <pe...@computer.org> wrote:
>> I've been re-reading the manual to try to gain a better understanding of
>> filters and handlers, specifically the difference between the two.
>>
>> The reason being -
>>
>> by default, the PHP interpreter is called as a handler (a typical
>> config: "AddHandler application/x-httpd-php .phtml".  By implementation
>> INCLUDES is a filter which is enabled using e.g.
>> "AddOutputFilter INCLUDES shtml".
>>
>> I'd like to have my files processed first by the INCLUDES filter, then
>> by the PHP handler.  The "AddOutputFilter" option clearly supports this
>> type of sequence.
>>
>> But back to my initial question - what is the functional difference
>> between a handler and a filter?
> 
> Handlers must originate the content themselves, whereas filters can
> deal with content passed down from someplace else.
> 
> PHP is only a handler, due to zend's requirement that it deal with the
> php file on disk and not in memory. (This was the argument at the
> time, anyway. I'm not sure if things in php land have evolved since
> that decision was made.) Therefore PHP must originate the content and
> can't act on content passed from someplace else like mod_include.

Substantially.  Thanks to John and I, and improvements in the Zend2
engine, it's quite a respectable filter now.

People are simply used to treating php as a handler.

That said; there can be only 1:1 handler for a request.  You can stack
many filters on top of that.

It's trivial to make a handler that is essentially printf("hello world!");

It's another thing to make a filter that decorates whatever comes up from
the core handler (e.g. "hello world!") and decorate it by processing it
in a scripting language or transforming it (e.g. into "<p>hello world!</p>"
or "HELLO WORLD!").

In a perfect world, there will be only a handful of handlers soon, such
as a filesystem handler, a database content record handler, etc.  Almost
everything else add-in modules do can be described as filtering, and once
they are a proper filter, things are much more pluggable.

---------------------------------------------------------------------
The official User-To-User support forum of the Apache HTTP Server Project.
See <URL:http://httpd.apache.org/userslist.html> for more info.
To unsubscribe, e-mail: users-unsubscribe@httpd.apache.org
   "   from the digest: users-digest-unsubscribe@httpd.apache.org
For additional commands, e-mail: users-help@httpd.apache.org