This article describes the major changes and improvements in smarty 3 comparing to smarty 2.
The Smarty 3 API (as of beta 8 ) has been refactored to a syntax geared for consistency and modularity. The Smarty 2 API syntax is still supported, butwill throw a deprecation notice. You can disable the notices, but it is highly recommended to adjust your syntax to Smarty 3, as the Smarty 2 syntax must run through an extra rerouting wrapper.
Basically, all Smarty methods now follow the "fooBarBaz" camel case syntax. Also, all Smarty properties now have getters and setters. So for example, the property $smarty->cache_dir can be set with $smarty->setCacheDir('foo/') and can be retrieved with $smarty->getCacheDir(). Some of the Smarty 3 APIs have been revoked such as the "is*" methods that were just duplicate functions of the now available "get*" methods.However, Smarty 3 works completely different on the inside. Smarty 3 is mostly backward compatible with Smarty 2, except for the following items:
* Smarty 3 is PHP 5 only. It will not work with PHP 4.
* The {php} tag is disabled by default. Enable with $smarty->allow_php_tag=true.
* Delimiters surrounded by whitespace are no longer treated as Smarty tags.
Therefore, { foo } will not compile as a tag, you must use {foo}. This change Makes Javascript/CSS easier to work with, eliminating the need for {literal}. This can be disabled by setting smarty->auto_literal = false;
* The Smarty 3 API is a bit different. Many Smarty 2 API calls are deprecated but still work. You will want to update your calls to Smarty 3 for maximum efficiency.
The Smarty 3 file structure is similar to Smarty 2:


A lot of Smarty 3 core functionality lies in the sysplugins directory; you do not need to change any files here. The /libs/plugins/ folder is where Smarty plugins are located. You can add your own here, or  create a separate plugin directory, just the same as Smarty 2. You will still need to create your own /cache/, /templates/, /templates_c/, /configs/ folders. Be sure /cache/ and /templates_c/ are writable. The typical way to use Smarty 3 should also look familiar:

$smarty = new Smarty;

There are many things that are new to Smarty 3. Here are the notable items:
Smarty 3 now uses a lexing tokenizer for its parser/compiler. Basically, this means Smarty has some syntax additions that make life easier such as in-template math, shorter/intuitive function parameter options, infinite function recursion, more accurate error handling, etc.
Smarty 3 allows expressions almost anywhere. Expressions can include PHP functions as long as they are not disabled by the security policy, object methods and properties, etc. The {math} plugin is no longer necessary but is still supported for BC. Examples:

{$x+$y}                           will output the sum of x and y.
{$foo = strlen($bar)}             function in assignment
{assign var=foo value= $x+$y}     in attributes
{$foo = myfunct( ($x+$y)*3 )}     as function parameter
{$foo[$x+3]}                      as array index

Smarty tags can be used as values within other tags. Example:  {$foo={counter}+3} Smarty tags can also be used inside double quoted strings. Example: {$foo="this is message {counter}"} You can define arrays within templates. Examples:

{assign var=foo value=[1,2,3]}
{assign var=foo value=['y'=>'yellow','b'=>'blue']}

Arrays can be nested.
{assign var=foo value=[1,[9,8],3]} You can assign a value to a specific array element. If the variable exists but is not an array, it is converted to an array before the new values are assigned. Examples:


You can append values to an array. If the variable exists but is not an array, it is converted to an array before the new values are assigned. Example: {$foo[]=1} You can use a PHP-like syntax for accessing array elements, as well as the original "dot" notation. Examples:

{$foo[1]}             normal access
{$foo['bar']}{$foo['bar'][1]}{$foo[$x+$x]}         index may contain any expression
{$foo[$bar[1]]}       nested index
{$foo[section_name]}  smarty section access, not array access!

The original "dot" notation stays, and with improvements. Examples:

{$foo.a.b.c}        =>  $foo['a']['b']['c']
{$foo.a.$b.c}       =>  $foo['a'][$b]['c']        with variable index
{$foo.a.{$b+4}.c}   =>  $foo['a'][$b+4]['c']       with expression as index
{$foo.a.{$b.c}}     =>  $foo['a'][$b['c']]         with nested index

note that { and } are used to address ambiguties when nesting the dot syntax. Variable names themselves can be variable and contain expressions. Examples:

$foo         normal variable
$foo_{$bar}  variable name containing other variable
$foo_{$x+$y} variable name containing expressions
$foo_{$bar}_buh_{$blar}  variable name with multiple segments
{$foo_{$x}}  will output the variable
$foo_1 if $x has a value of 1.

Object method chaining is implemented.

{for} tag added for looping (replacement for {section} tag)
{for $x=0, $y=count($foo); $x<$y; $x++}  ....  {/for}

Any number of statements can be used separated by comma as the first inital expression at {for}.
{for $x = $start to $end step $step} ... {/for}is in the SVN now .
You can use also
{for $x = $start to $end} ... {/for}
In this case the step value will be automaticall 1 or -1 depending on the start and end values. Instead of $start and $end you can use any valid expression. Inside the loop the following special vars can be accessed:

$x@iteration = number of iteration
$x@total = total number of iterations
$x@first = true on first iteration
$x@last = true on last iteration

The Smarty 2 {section} syntax is still supported. New shorter {foreach} syntax to loop over an array. Example: {foreach $myarray as $var}...{/foreach} Within the foreach loop, properties are access via: $var@key foreach $var array key $var@iteration foreach current iteration count (1,2,3...) $var@index          foreach current index count (0,1,2...) $var@total          foreach $var array total $var@first          true on first iteration $var@last           true on last iteration The Smarty 2 {foreach} tag syntax is still supported. NOTE: {$bar[foo]} still indicates a variable inside of a {section} named foo. If you want to acces s an array element with index foo, you must use quotes such as {$bar['foo']}, or use the dot syntax {$}. while block tag is now implemented:

{while $foo}...{/while}
{while $x lt 10}...{/while}

Direct access to PHP functions:
Just as you can use PHP functions as modifiers directly, you can now access PHP functions directly, provided they are permitted by security settings:


There is a new {function}...{/function} block tag to implement a template function. This enables reuse of code sequences like a plugin function. It can call itself recursively. Template function must be called with the new {call...} tag. Example:

{function level=0}
< ul >
{foreach $data as $entry}
{if is_array($entry)}
    < li >{$entry@key}< /li >
{call data=$entry level=$level+1}{else}
    < li >{$entry}</ li >
</ ul >
{$menu = ['item1','item2','item3' => ['item3-1','item3-2','item3-3' =>
['item3-3-1','item3-3-2']],'item4']}{call data=$menu}

Generated output:

* item1
* item2
* item3
   o item3-1
   o item3-2
   o item3-3
      + item3-3-1
      + item3-3-2
* item4

The function tag itself must have the "name" attribute. This name is the tag name when calling the function. The function tag may have any number of additional attributes. These will be default settings for local variables.
New {nocache} block function:
{nocache}...{/nocache} will declare a section of the template to be non-cached when template caching is enabled.
New nocache attribute:
You can declare variable/function output as non-cached with the nocache attribute. Examples:

{$foo nocache=true}
{$foo nocache} /* same */
{foo bar="baz" nocache=true}
{foo bar="baz" nocache} /* same */
{time() nocache=true}
{time() nocache} /* same */

Or you can also assign the variable in your script as nocache:

$smarty->assign('foo',$something,true); // third param is nocache setting
{$foo} /* non-cached */

$smarty.current_dir returns the directory name of the current template. You can use strings directly as templates with the "string" resource type. Examples:

$smarty->display('string:This is my template, {$foo}!'); // php
{include file="string:This is my template, {$foo}!"} // template

In Smarty 2, all assigned variables were stored within the Smarty object. Therefore, all variables assigned in PHP were accessible by all subsequent fetch and display template calls. In Smarty 3, we have the choice to assign variables to the main Smarty object, to user-created data objects, and to user-created template objects. These objects can be chained. The object at the end of a chain can access all variables belonging to that template and all variables within the parent objects. The Smarty object can only be the root of a chain, but a chain can be isolated from the Smarty object. All known Smarty assignment interfaces will work on the data and template objects. Besides the above mentioned objects, there is also a special storage area for global variables. A Smarty data object can be created as follows:

$data = $smarty->createData(); // create root data objec
t$data->assign('foo','bar');       // assign variables as usual
$data->config_load('my.conf');   // load config file
$data= $smarty->createData($smarty);  // create data object having a parent link to the Smarty object
$data2= $smarty->createData($data);   // create data object having a parent link to the
$data data object

A template object can be created by using the createTemplate method. It has the same parameter assignments as the fetch() or display() method.
Function definition:
function createTemplate($template, $cache_id = null, $compile_id = null, $parent = null) The first parameter can be a template name, a smarty object or a data object. Examples:

$tpl = $smarty->createTemplate('mytpl.tpl'); // create template object not linked to any parent
$tpl->assign('foo','bar');           // directly assign variables
$tpl->config_load('my.conf'); // load config file
$tpl = $smarty->createTemplate('mytpl.tpl',$smarty);  // create template having a parent link to the Smarty object
$tpl = $smarty->createTemplate('mytpl.tpl',$data);    // create template having a parent link to the $data object

The standard fetch() and display() methods will implicitly create a template object. If the $parent parameter is not specified in these method calls, the template object is will link back to the Smarty object as it's parent. If a template is called by an {include...} tag from another template, the subtemplate links back to the calling template as it's parent. All variables assigned locally or from a parent template are accessible. If the template creates or modifies a variable by using the {assign var=foo...} or {$foo=...} tags, these new values are only known locally (local scope). When the template exits, none of the new variables or modifications can be seen in the parent template(s). This is same behavior as in Smarty 2. With Smarty 3, we can assign variables with a scope attribute which allows the availablility of these new variables or modifications globally (ie in the parent templates.) Possible scopes are local, parent, root and global. Examples:

{assign var=foo value='bar'}       // no scope is specified, the default 'local'
{$foo='bar'}                       // same, local scope
{assign var=foo value='bar' scope='local'} // same, local scope
{assign var=foo value='bar' scope='parent'} // Values will be available to the parent object
{$foo='bar' scope='parent'}                 // (normally the calling template)
{assign var=foo value='bar' scope='root'}   // Values will be exported up to the root object, so they can
{$foo='bar' scope='root'}                   // be seen from all templates using the same root.
{assign var=foo value='bar' scope='global'} // Values will be exported to global variable storage,
{$foo='bar' scope='global'}                 // they are available to any and all templates.

The scope attribute can also be attached to the {include...} tag. In this case, the specified scope will be the default scope for all assignments within the included template.
Smarty3 are following the same coding rules as in Smarty2. The only difference is that the template object is passed as additional third parameter. smarty_plugintype_name (array $params, object $smarty, object $template). The Smarty 2 plugins are still compatible as long as they do not make use of specific Smarty2 internals.
With template inheritance you can define blocks, which are areas that can be overriden by child templates, so your templates could look like this:

< html >
< head >
{block name='title'}My site name{/block}
< / head >
< body >
< h1 >{block name='page-title'}Default page title{/block}< / h1 >
< div id="content" >
{block name='content'}
Default content
< /div >
< /body >
< /html >
{extends file='parent.tpl'}
{block name='title'}
Child title
{extends file='child.tpl'}
{block name='title'}Home - {$smarty.block.parent}{/block}
{block name='page-title'}My home{/block}
{block name='content'}
{foreach $images as $img}
< img src="{$img.url}" alt="{$img.description}" / >

We redefined all the blocks here, however in the title block we used { $smarty.block.parent}, which tells Smarty to insert the default content from the parent template in its place. The content block was overriden to display the image files, and page-title has also be overriden to display a completely different title. If we render grandchild.tpl we will get this: < html > < head > < title >Home - Child title < /title > < /head > < body > < h1 >My home< /h1 > < div id="content" > < img src="/example.jpg" alt="image" / > < img src="/example2.jpg" alt="image" / > < img src="/example3.jpg" alt="image" / > < / div > < /body > < /html > NOTE: In the child templates everything outside the {extends} or {block} tag sections is ignored.The inheritance tree can be as big as you want (meaning you can extend a file that extends another one that extends another one and so on..), but be aware that all files have to be checked for modifications at runtime so the more inheritance the more overhead you add. Instead of defining the parent/child relationships with the {extends} tag in the child template youcan use the resource as follow: $smarty->display('extends:parent.tpl|child.tpl|grandchild.tpl'); Child {block} tags may optionally have a append or prepend attribute. In this case the parent block content is appended or prepended to the child block content. {block name='title' append} My title {/block}
For those that prefer pure PHP over the {tag} based syntax, Smarty now offers a PHP option for template syntax. PHP templates have several differences over the tag-based templates: *) PHP templates are not compiled, they are included directly by the engine. *) None of Smarty's security features are applied to PHP templates. *) By default, PHP templates are disabled, set $smarty->allow_php_templates=true. If you want to use a PHP template, just use the "php" resource type: $smarty->display('php:foo.php'); You can also mix PHP templates with {tag} templates: {include file="php:foo.php"} In PHP templates, assigned vars are available simply as:

// same as {$foo}
< ?php echo $foo; ? >
< ?=$foo? > // php short tags

At this point, smarty modifier/function plugins are not conveniently accessible from PHP templates. A wrapper function may become available in the future. You can call PHP functions a usual:
You can register a class with optional namespace for the use in the template like: $smarty->register->templateClass('foo','name\name2\myclass'); In the template you can use it like this: {foo::method()}  etc.

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