Chapter 1. What is Smarty?
Smarty is a template engine for PHP. More specifically, it facilitates a
manageable way to separate application logic and content from its
presentation. This is best described in a situation where the application
programmer and the template designer play different roles, or in most cases
are not the same person. For example, let's say you are creating a web page
that is displaying a newspaper article. The article headline, tagline,
author and body are content elements, they contain no information about how
they will be presented. They are passed into Smarty by the application,
then the template designer edits the templates and uses a combination of
HTML tags and template tags to format the presentation of these elements
(HTML tables, background colors, font sizes, style sheets, etc.) One day
the programmer needs to change the way the article content is retrieved (a
change in application logic.) This change does not affect the template
designer, the content will still arrive in the template exactly the same.
Likewise, if the template designer wants to completely redesign the
templates, this requires no changes to the application logic. Therefore,
the programmer can make changes to the application logic without the need
to restructure templates, and the template designer can make changes to
templates without breaking application logic.
One design goal of Smarty is the separation of business logic and
presentation logic. This means templates can certainly contain logic under
the condition that it is for presentation only. Things such as including
other templates, altering table row colors, upper-casing a variable,
looping over an array of data and displaying it, etc. are all examples of
presentation logic. This does not mean that Smarty forces a separation of
business and presentation logic. Smarty has no knowledge of which is which,
so placing business logic in the template is your own doing. Also, if you
desire NO logic in your templates you certainly can do so by boiling the
content down to text and variables only.
One of the unique aspects about Smarty is the template compling. This means
Smarty reads the template files and creates PHP scripts from them. Once
they are created, they are executed from then on. Therefore there is no
costly template file parsing for each request, and each template can take
full advantage of PHP compiler cache solutions such as Zend Accelerator
(http://www.zend.com/) or PHP Accelerator
(http://www.php-accelerator.co.uk).
Some of Smarty's features:
It is extremely fast.
It is efficient since the PHP parser does the dirty work.
No template parsing overhead, only compiles once.
It is smart about recompiling only the template files that have changed.
You can make custom functions
and custom variable modifiers, so the
template language is extremely extensible.
Configurable template delimiter tag syntax, so you can use
{}, {{}}, <!--{}-->, etc.
The if/elseif/else/endif constructs are passed to the
PHP parser, so the {if ...} expression syntax can be as simple or as complex
as you like.
Unlimited nesting of sections, ifs, etc. allowed.
It is possible to embed PHP code right in your template files,
although this may not be needed (nor recommended)
since the engine is so customizable.
Built-in caching support
Arbitrary template sources
Custom cache handling functions
Plugin architecture
