Posted by Mattias Thorslund on 04/30/05 04:09

Rasmus Lerdorf wrote:

> Mattias Thorslund wrote:
>
>> Who says PHP itself is a template engine? I think nobody.
>
>
> I do.
>
> It comes down to whether you want the delineation between the template
> and the business logic enforced by the system or not. PHP is a
> general-purpose templating system that does not enforce this
> delineation.



That explanation is sensible enough.


[skipping ahead a little]

> The approach I tend to point people at is something I have been
> calling a Template API. That is, when you build your application, you
> create a template api to go along with it. In essence you are
> creating a templating system for each application you write.


For many projects, I think the approach you describe in the example
(below) is appropriate. One nice thing is that output can begin before
the whole page has been nearly processed. I don't know if many other
templating solutions can do that.

To me, it looks like it would be hard to keep the functions that are
called by the template to a reasonable format or number, at least in a
larger project. If it's a template that is to be used by many kinds of
pages, there would be either a large number of functions, or there would
be generic functions that need to do different things based on the
situation.

Of course, the functions could become methods of a "page" object. Then,
it gets easy to create specialized subclasses of page objects which can
respond differently to the same generic method call. Sounds more
attractive the more I think about it :-)

Then again, if I need a big object to handle the business logic (and
dynamic presentation logic) because my template approach is sequential,
it might be a toss-up compared to using sequential business logic and a
small template object.


> For example, I describe a simple such system here:
>
> http://talks.php.net/show/mtladv05/20
>
> To me, this is a perfectly good template (from the slide):
>
> <?php
> start_poll(1);
> $os = array("FreeBSD","Linux","OSX","Windows","Other");
> ?>
> <p class="purpose">
> Please answer a couple of questions for us.
> </p>
>
> <p class="question">
> 1. What is your name?
> </p>
> <?php text_answer('name',64)?>
>
> <p class="question">
> 2. Which operating systems do you use on a daily basis?
> </p>
> <?php select_any_of($os)?>
>
> <p class="question">
> 3. Which operating system do you prefer?
> </p>
> <?php select_one_of($os)?>
>
> <?php end_poll(); ?>
>
> The end_poll() call could be eliminated as well to make it slightly
> cleaner, but otherwise this is straight-forward with no mixing of
> business-logic and content.

>
> My main issue with general-purpose templating systems is that they
> always end up inventing a new language.


Except the class described in the article I was talking about. It uses
PHP as the template language. It's a big reason why I find it attractive.

[skipping discussion on Smarty]

> As far as I am concerned you shouldn't be dealing with any sort of
> objects from a template to begin with.


This does place some demands on the business logic.

> There should be nothing but simple variables and straight function
> calls from a template, but this is a religious issue that people will
> never agree on. Hence PHP's neutral approach where the exact
> templating delienation is left up to the users.


No doubt, people will continue to argue over it for a long time to
come. I try not to be religious about it, I simply want to know as many
sides of the issue as possible.

Best,

Mattias


--
More views at http://www.thorslund.us

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