108 lines
4.8 KiB
Markdown
108 lines
4.8 KiB
Markdown
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# Philosophy
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## What is Smarty?
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Smarty is a template engine for PHP. More specifically, it facilitates a
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manageable way to separate application logic and content from its
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presentation. This is best described in a situation where the
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application programmer and the template designer play different roles,
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or in most cases are not the same person.
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For example, let's say you are creating a web page that is displaying a
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newspaper article.
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- The article `$headline`, `$tagline`, `$author` and `$body` are
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content elements, they contain no information about how they will be
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presented. They are [passed](getting-started.md#basic-usage) into Smarty by the
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application.
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- Then the template designer edits the templates and uses a
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combination of HTML tags and [template tags](designers/language-basic-syntax/language-syntax-tags.md)
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to format the presentation of these
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[variables](designers/language-basic-syntax/language-syntax-variables.md) with elements such as
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tables, div\'s, background colors, font sizes, style sheets, svg
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etc.
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- One day the programmer needs to change the way the article content
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is retrieved, ie a change in application logic. This change does not
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affect the template designer, the content will still arrive in the
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template exactly the same.
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- Likewise, if the template designer wants to completely redesign the
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templates, this would require no change to the application logic.
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- Therefore, the programmer can make changes to the application logic
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without the need to restructure templates, and the template designer
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can make changes to templates without breaking application logic.
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## Goals
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The Smarty design was largely driven by these goals:
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- clean separation of presentation from application code
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- PHP backend, Smarty template frontend
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- complement PHP, not replace it
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- fast development/deployment for programmers and designers
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- quick and easy to maintain
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- syntax easy to understand, no PHP knowledge necessary
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- flexibility for custom development
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- security: insulation from PHP
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- free, open source
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## Two camps of thought
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When it comes to templating in PHP, there are basically two camps of
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thought. The first camp exclaims that \"PHP is a template engine\". This
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approach simply mixes PHP code with HTML. Although this approach is
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fastest from a pure script-execution point of view, many would argue
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that the PHP syntax is messy and complicated when mixed with tagged
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markup such as HTML.
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The second camp exclaims that presentation should be void of all
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programming code, and instead use simple tags to indicate where
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application content is revealed. This approach is common with other
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template engines (even in other programming languages), and is also the
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approach that Smarty takes. The idea is to keep the templates focused
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squarely on presentation, void of application code, and with as little
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overhead as possible.
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## Why is separating PHP from templates important?
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Two major benefits:
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- SYNTAX: Templates typically consist of semantic markup such as HTML.
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PHP syntax works well for application code, but quickly degenerates
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when mixed with HTML. Smarty\'s simple {tag} syntax is designed
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specifically to express presentation. Smarty focuses your templates
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on presentation and less on \"code\". This lends to quicker template
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deployment and easier maintenance. Smarty syntax requires no working
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knowledge of PHP, and is intuitive for programmers and
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non-programmers alike.
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- INSULATION: When PHP is mixed with templates, there are no
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restrictions on what type of logic can be injected into a template.
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Smarty insulates the templates from PHP, creating a controlled
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separation of presentation from business logic. Smarty also has
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security features that can further enforce restrictions on
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templates.
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## Web designers and PHP
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A common question: "Web designers have to learn a syntax anyway, why
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not PHP?" Of course web designers can learn PHP, and they may already
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be familiar with it. The issue isn't their ability to learn PHP, it is
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about the consequences of mixing PHP with HTML. If designers use PHP, it
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is too easy to add code into templates that doesn't belong there (you
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just handed them a swiss-army knife when they just needed a knife.) You
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can teach them the rules of application design, but this is probably
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something they don't really need to learn (now they are developers!)
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The PHP manual is also an overwhelming pile of information to sift
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through. It is like handing the owner of a car the factory assembly
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manual when all they need is the owners manual. Smarty gives web
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designers exactly the tools they need, and gives developers fine-grained
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control over those tools. The simplicity of the tag-based syntax is also
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a huge welcome for designers, it helps them streamline the organization
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and management of templates.
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