Syntax
******

.[perex]
Syntax Latte was born out of the practical requirements of web designers. We were looking for the most user-friendly syntax, with which you can elegantly write constructs that are otherwise a real challenge.
At the same time, all expressions are written exactly the same as in PHP, so you don't have to learn a new language. You just make the most of what you already know.

Below is a minimal template that illustrates a few basics elements: tags, n:attributes, comments and filters.

```latte
{* this is a comment *}
<ul n:if="$items">                {* n:if is n:atribut *}
{foreach $items as $item}         {* tag representing foreach loop *}
	<li>{$item|capitalize}</li>   {* tag that prints a variable with a filter *}
{/foreach}                        {* end of cycle *}
</ul>
```

Let's take a closer look at these important elements and how they can help you build an incredible template.


Tags
====

A template contains tags that control the template logic (for example, *foreach* loops) or output expressions. For both, a single delimiter `{ ... }` is used, so you don't have to think about which delimiter to use in which situation, as with other systems.
If the `{` character is followed by a quote or space, Latte doesn't consider it to be the beginning of a tag, so you can use JavaScript constructs, JSON, or CSS rules in your templates without any problems.

See [overview of all tags|tags]. In addition, you can also create [custom tags|extending-latte#tags].


Latte Understands PHP
=====================

You can use PHP expressions that you know well inside the tags:

- variables
- strings (including HEREDOC and NOWDOC), arrays, numbers, etc.
- [operators |https://www.php.net/manual/en/language.operators.php]
- function and method calls (which can be restricted by [sandbox])
- [match |https://www.php.net/manual/en/control-structures.match.php]
- [anonymous functions |https://www.php.net/manual/en/functions.arrow.php]
- [callbacks |https://www.php.net/manual/en/functions.first_class_callable_syntax.php]
- multi-line comments `/* ... */`
- etc...

In addition, Latte adds several [nice extensions |#Syntactic Sugar] to the PHP syntax.


n:attributes
============

Each pair tag, such as `{if} … {/if}`, operating upon single HTML element can be written in [n:attribute |#n:attribute] notation. For example, `{foreach}` in the above example could also be written this way:

```latte
<ul n:if="$items">
	<li n:foreach="$items as $item">{$item|capitalize}</li>
</ul>
```

The functionality then corresponds to the HTML element in which it is written:

```latte
{var $items = ['I', '♥', 'Latte']}

<p n:foreach="$items as $item">{$item}</p>
```

Prints:

```latte
<p>I</p>
<p>♥</p>
<p>Latte</p>
```

By using `inner-` prefix we can alter the behavior so that the functionality applies only to the body of the element:

```latte
<div n:inner-foreach="$items as $item">
	<p>{$item}</p>
	<hr>
</div>
```

Prints:

```latte
<div>
	<p>I</p>
	<hr>
	<p>♥</p>
	<hr>
	<p>Latte</p>
	<hr>
</div>
```

Or by using `tag-` prefix the functionality is applied on the HTML tags only:

```latte
<p><a href="{$url}" n:tag-if="$url">Title</a></p>
```

Depending on the value of `$url` variable this will print:

```latte
// when $url is empty
<p>Title</p>

// when $url equals 'https://nette.org'
<p><a href="https://nette.org">Title</a></p>
```

However, n:attributes are not only a shortcut for pair tags, there are some pure n:attributes as well, for example the coder's best friend [n:class|tags#n:class].


Filters
=======

See the summary of [standard filters|filters].

Latte allows calling filters by using the pipe sign notation (preceding space is allowed):

```latte
<h1>{$heading|upper}</h1>
```

Filters can be chained, in that case they apply in order from left to right:

```latte
<h1>{$heading|lower|capitalize}</h1>
```

Parameters are put after the filter name separated by colon or comma:

```latte
<h1>{$heading|truncate:20,''}</h1>
```

Filters can be applied on expression:

```latte
{var $name = ($title|upper) . ($subtitle|lower)}
```

On block:

```latte
<h1>{block |lower}{$heading}{/block}</h1>
```

Or directly on value (in combination with [`{=expr}`| https://latte.nette.org/en/tags#printing] tag):
```latte
<h1>{='  Hello world  '|trim}<h1>
```


Comments
========

Comments are written this way and do not get into the output:

```latte
{* this is a comment in Latte *}
```

PHP comments work inside tags:

```latte
{include 'file.info', /* value: 123 */}
```


Syntactic Sugar
===============


Strings Without Quotation Marks
-------------------------------

Quotation marks can be omitted for simple strings:

```latte
as in PHP:   {var $arr = ['hello', 'btn--default', '€']}

abbreviated: {var $arr = [hello, btn--default, €]}
```

Simple strings are those that are made up purely of letters, digits, underscores, hyphens and periods. They must not begin with a digit and must not begin or end with a hyphen.
It must not be composed of only uppercase letters and underscores, because then it is considered a constant (e.g. `PHP_VERSION`).
And it must not collide with the keywords `and`, `array`, `clone`, `default`, `false`, `in`, `instanceof`, `new`, `null`, `or`, `return`, `true`, `xor`.


Short Ternary Operator
----------------------

If the third value of the ternary operator is empty, it can be omitted:

```latte
as in PHP:   {$stock ? 'In stock' : ''}

abbreviated: {$stock ? 'In stock'}
```


Modern Key Notation in the Array
--------------------------------

Array keys can be written similarly to named parameters when calling functions:

```latte
as in PHP:   {var $arr = ['one' => 'item 1', 'two' => 'item 2']}

modern:      {var $arr = [one: 'item 1', two: 'item 2']}
```


Filters
-------

Filters can be used for any expression, just enclose the whole in brackets:

```latte
{var $content = ($text|truncate: 30|upper)}
```


Operator `in`
-------------

The `in` operator can be used to replace the `in_array()` function. The comparison is always strict:

```latte
{* like in_array($item, $items, true) *}
{if $item in $items}
	...
{/if}
```


.{data-version:2.9}
Optional Chaining with Undefined-Safe Operator
----------------------------------------------

The undefined-safe operator `??->` is similar to the nullsafe operator `?->`, but does not raise an error if a variable, property, or index does not exist at all.

```latte
{$order??->id}
```

this is a way of saying that when `$order` is defined and not null, `$order->id` will be computed, but when `$order` is null or doesn't exist, stop what we’re doing and just return null.

```latte
{$user??->address??->street}
// roughly means isset($user) && isset($user->address) ? $user->address->street : null
```


A Window into History
---------------------

Latte has come up with a number of syntactic candies over the course of its history, which appeared in PHP itself a few years later. For example, in Latte it was possible to write arrays as `[1, 2, 3]` instead of `array(1, 2, 3)` or use the nullsafe operator `$obj?->foo` long before it was possible in PHP itself. Latte also introduced the array expansion operator `(expand) $arr`, which is the equivalent of today's `...$arr` operator from PHP.


PHP Limitations in Latte
========================

Only PHP expressions can be written in Latte. That is, statements ending with a semicolon cannot be used. You cannot declare classes or use [control structures |https://www.php.net/manual/en/language.control-structures.php], such as `if`, `foreach`, `switch`, `return`, `try`, `throw` and others, instead of which Latte offers its [tags].
You also can't use [attributes |https://www.php.net/manual/en/language.attributes.php], [backticks |https://www.php.net/manual/en/language.operators.execution.php] or [magic constants |https://www.php.net/manual/en/language.constants.magic.php], because that wouldn't make sense.
You can't even use `unset`, `echo`, `include`, `require`, `exit`, `eval`, because they are not functions, but special PHP language constructs, and thus not expressions.

However, you can work around these limitations by activating the [RawPhpExtension |develop#RawPhpExtension] extension, which allows you to use any PHP code in the `{php ...}` tag at the responsibility of the template author.