On PhpPatterns, I recently read an
article on Template Engines in PHP. It got my ire up, as it said (my
interpretation):
- "template engines are a bad idea"
- "templating using PHP natively can be a good idea"
- "template engines... are not worth the text
their written in"
Okay, so that's actually direct quotes from the article. I took issue with
it, immediately -- I use Smarty for
everything I do, and the decision to do so was not done lightly. I have in
fact been advocating the use of template engines in one language or another
for several years with the various positions in which I've been employed; I
think they are an essential tool for projects larger than a few pages. Why?
- Mixing of languages causes inefficiency. When I'm programming, it's
incredibly inefficient to be writing in up to four different languages: PHP
or Perl, X/HTML, CSS, and Javascript. Switching between them while in the
same file is cumbersome and confusing, and trying to find HTML entities
buried within quoting can be a nightmare, even when done in heredocs.
Separating the languages into different files seems not only natural, but
essential.
- Views contain their own logic. In an MVC pattern, the final web page
View may be dependent on data passed to it via the Controller; however,
this doesn't mean that I want the full functionality of a language like PHP
or Perl to do that. I should only be doing simple logic or looping
constructs -- and a full scripting language is overkill. (I do recognize,
however, that template engines such as Smarty are written using PHP, so the
language is being invoked regardless. What I speak of here is the language
used to compose the template.)
- Abstraction and Security. The fewer internals that are divulged on the
template page, the better. For security purposes, I may not want clients
able to know how data got to the page, only what data is available
to them. In addition, if this data is abstracted enough, any number of
backends could be connected to the page to produce output.
So, reading the aforementioned article really got my hackles up. However, it
got me thinking, as well. One issue raised is that PHP can be used as your
templating language. While I can understand why this might be desirable --
everything from load issues to flexibility -- I also feel that this doesn't
give enough abstraction.
Using PHP seems to me to be inefficient on two fundamental levels, based on
my understanding of The Pragmatic Programmer:
- Domain Langauge. The Pragmatic Programmer suggests that
subsets of a language should be used, or wholly new mini-languages
developed, that speak to the domain at hand. As an example, you might want
to use a sharp tool to open a can; an axe would be overkill, but a knife
might work nicely. Using PHP to describe a template is like using an axe to
open a can; it'll do the job, but it may also make a mess of it all, simply
because it's too much sharp edge for the job.
- Metadata. Metadata is data about data; to my thinking, templates
describe the data they are communicating; the compiled template actually
contains the data. In this regard, again, putting PHP into the script is
overkill as doing so gives more than just some hints as to what the data
is.
The author of the article also makes a case for teaching web designers PHP
-- that the language is sufficiently easy to pick up that they typically
will be able to learn it as easily, if not more easily, than a template
language. I agree to a degree... But my experience has shown that web
designers typically struggle with HTML, let alone PHP. (Note: my experience
in this regard is not huge, and I'm sure that this is an exaggeration.) I
find that it's typically easiest for me to give an example template, explain
what the funny, non-HTML stuff can do, and let them go from there. Using
this approach, they do not need to learn anything new -- they simply work
with placeholders.
Still, I think the author raises some fine points. I wish he'd bothered to
do more research into why people choose template engines and the
benefits that arise from using them before simply outright slamming
them. Of course, the article is also a bit dated; it was written over two
years ago, and much has changed in the world of PHP and many of its template
engines. I'm curious as to whether they would feel the same way today.
Me? My mind is made up -- the benefits, in my circumstances, far outweigh
any costs associated. I'll be using template engines, and Smarty in particular, for years to
come.
