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 variables with elements such as tables, div's, background colors, font sizes, style sheets, svg etc. One day the programmer needs to change the way the article content is retrieved, ie 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 would require no change 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, alternating table row colors, upper-casing a variable, looping over an array of data and displaying it are examples of presentation logic. This does not mean however 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 compiling. 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. Each template can take full advantage of PHP compiler and cache solutions such as eAccelerator, ionCube mmCache or Zend Accelerator to name a few. 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 easily create your own custom functions and variable modifiers, so the template language is extremely extensible. Configurable template {delimiter} tag syntax, so you can use {$foo}, {{$foo}}, <!--{$foo}-->, etc. The {if}..{elseif}..{else}..{/if} constructs are passed to the PHP parser, so the {if...} expression syntax can be as simple or as complex an evaluation as you like. Allows unlimited nesting of sections, if's etc. 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 Smarty requires a web server running PHP 4.0.6 or greater. Install the Smarty library files which are in the /libs/ sub directory of the distribution. These are .php files that you SHOULD NOT edit. They are shared among all applications and only get changed when you upgrade to a new version of Smarty. In the examples below the Smarty tarball has been unpacked to: /usr/local/lib/Smarty-v.e.r/ for *nix machines and c:\webroot\libs\Smarty-v.e.r\ for the windows enviroment. Smarty uses a PHP constant named SMARTY_DIR which is the full system file path to the Smarty libs/ directory. Basically, if your application can find the Smarty.class.php file, you do not need to set the SMARTY_DIR as Smarty will figure it out on its own. Therefore, if Smarty.class.php is not in your include_path, or you do not supply an absolute path to it in your application, then you must define SMARTY_DIR manually. SMARTY_DIR must include a trailing slash/. Here's how you create an instance of Smarty in your PHP scripts: ]]> Try running the above script. If you get an error saying the Smarty.class.php file could not be found, you need to do one of the following: ]]> ]]> ]]> Now that the library files are in place, it's time to setup the Smarty directories for your application: Smarty requires four directories which are by default named templates/, templates_c/, configs/ and cache/ Each of these are definable by the Smarty class properties $template_dir, $compile_dir, $config_dir, and $cache_dir respectively It is highly recommended that you setup a separate set of these directories for each application that will use Smarty For our installation example, we will be setting up the Smarty environment for a guest book application. We picked an application only for the purpose of a directory naming convention. You can use the same environment for any application, just replace guestbook/ with the name of your application. Be sure that you know the location of your web server's document root as a file path. In the following examples, the document root is /web/www.example.com/guestbook/htdocs/. The Smarty directories are only accessed by the Smarty library and never accessed directly by the web browser. Therefore to avoid any security concerns, it is recommended (but not mandatory) to place these directories outside of the web server's document root. You will need as least one file under your document root, and that is the script accessed by the web browser. We will name our script index.php, and place it in a subdirectory under the document root /htdocs/. Smarty will need write access (windows users please ignore) to the $compile_dir and $cache_dir directories (templates_c/ and cache/), so be sure the web server user account can write to them. This is usually user nobody and group nobody. For OS X users, the default is user www and group www. If you are using Apache, you can look in your httpd.conf file to see what user and group are being used. chmod 770 will be fairly tight security, it only allows user nobody and group nobody read/write access to the directories. If you would like to open up read access to anyone (mostly for your own convenience of viewing these files), you can use 775 instead. We need to create the index.tpl file that Smarty will display. This needs to be located in the $template_dir. {* Smarty *} is a template comment. It is not required, but it is good practice to start all your template files with this comment. It makes the file easy to recognize regardless of the file extension. For example, text editors could recognize the file and turn on special syntax highlighting. Now lets edit index.php. We'll create an instance of Smarty, assign() a template variable and display() the index.tpl file. template_dir = '/web/www.example.com/guestbook/templates/'; $smarty->compile_dir = '/web/www.example.com/guestbook/templates_c/'; $smarty->config_dir = '/web/www.example.com/guestbook/configs/'; $smarty->cache_dir = '/web/www.example.com/guestbook/cache/'; $smarty->assign('name','Ned'); //** un-comment the following line to show the debug console //$smarty->debugging = true; $smarty->display('index.tpl'); ?> ]]> In our example, we are setting absolute paths to all of the Smarty directories. If /web/www.example.com/guestbook/ is within your PHP include_path, then these settings are not necessary. However, it is more efficient and (from experience) less error-prone to set them to absolute paths. This ensures that Smarty is getting files from the directories you intended. Now naviagate to the index.php file with the web browser. You should see "Hello Ned, welcome to Smarty!" You have completed the basic setup for Smarty! This is a continuation of the basic installation, please read that first! A slightly more flexible way to setup Smarty is to extend the class and initialize your Smarty environment. So instead of repeatedly setting directory paths, assigning the same vars, etc., we can do that in one place. Lets create a new directory /php/includes/guestbook/ and make a new file called setup.php. In our example environment, /php/includes is in our include_path. Be sure you set this up too, or use absolute file paths. Smarty(); $this->template_dir = '/web/www.example.com/guestbook/templates/'; $this->compile_dir = '/web/www.example.com/guestbook/templates_c/'; $this->config_dir = '/web/www.example.com/guestbook/configs/'; $this->cache_dir = '/web/www.example.com/guestbook/cache/'; $this->caching = true; $this->assign('app_name', 'Guest Book'); } } ?> ]]> Now lets alter the index.php file to use setup.php: assign('name','Ned'); $smarty->display('index.tpl'); ?> ]]> Now you see it is quite simple to bring up an instance of Smarty, just use Smarty_GuestBook() which automatically initializes everything for our application.