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.