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 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, and each template can take full advantage of PHP compiler cache solutions such as Zend Accelerator (&url.zend;) or PHP Accelerator (&url.php-accelerator;). 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 Smarty requires a web server running PHP 4.0.6 or later. Install the Smarty library files which are in the /libs/ directory of the distribution. These are the PHP files that you SHOULD NOT edit. They are shared among all applications and they only get updated when you upgrade to a new version of Smarty. Smarty uses a PHP constant named SMARTY_DIR which is the system filepath Smarty library directory. Basically, if your application can find the Smarty.class.php file, you do not need to set SMARTY_DIR, 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 is 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 have 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. Be sure you know the location of your web server document root. In our example, the document root is /web/www.example.com/docs/. 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 to place these directories outside of the document root. 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 app. We'll place our Smarty directories under /web/www.example.com/smarty/guestbook/. You will need as least one file under your document root, and that is the script accessed by the web browser. We will call our script index.php, and place it in a subdirectory under the document root called /guestbook/. It is convenient to setup the web server so that "index.php" can be identified as the default directory index, so if you access "http://www.example.com/guestbook/", the index.php script will be executed without "index.php" in the URL. In Apache you can set this up by adding "index.php" onto the end of your DirectoryIndex setting (separate each entry with a space.) Lets take a look at the file structure so far: Smarty will need write access to the $compile_dir and $cache_dir, so be sure the web server user 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 (usually in "/usr/local/apache/conf/") 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 load. This will be located in your $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. In our example environment, "/usr/local/lib/php/Smarty" is in our include_path. Be sure you do the same, or use absolute paths. template_dir = '/web/www.example.com/smarty/guestbook/templates/'; $smarty->compile_dir = '/web/www.example.com/smarty/guestbook/templates_c/'; $smarty->config_dir = '/web/www.example.com/smarty/guestbook/configs/'; $smarty->cache_dir = '/web/www.example.com/smarty/guestbook/cache/'; $smarty->assign('name','Ned'); $smarty->display('index.tpl'); ?> ]]> In our example, we are setting absolute paths to all of the Smarty directories. If /web/www.example.com/smarty/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 load the index.php file from your web browser. You should see "Hello, Ned!" 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/smarty/guestbook/templates/'; $this->compile_dir = '/web/www.example.com/smarty/guestbook/templates_c/'; $this->config_dir = '/web/www.example.com/smarty/guestbook/configs/'; $this->cache_dir = '/web/www.example.com/smarty/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.