# Templates with Plates
## Template
To separate HTML code and PHP code it's possible to use **templates** with markers for variable substitution.
Variables are created in the PHP code and are passed to the template in the **rendering** phase.
The server transmits only the `index.php` file to the user. The php file renders the templates as needed.
```html
<html>
<head>
<title><?= $this->e($title)?></title>
</head>
<body>
<?= $this->section('content')?>
</body>
</html>
```
## [Plates](https://platesphp.com/)
Plates is a template engine for PHP. A template engine permits to separate the PHP code (business logic) from the HTML pages.
Installation through composer: `composer require league/plates`.
```php
# index.php
require "vendor/autoload.php";
use League\Plates\Engine;
$templates = new Engine("path\\to\\templates");
echo $templates->render("template_name", [
"key_1" => "value_1",
"key_2" => "value_2"
]);
```
```php
# template.php
<html>
<head>
<title><?= $key_1?></title>
</head>
<body>
<h1>Hello <?= $key_2 ?></h1>
</body>
</html>
```
Variables in the template are created through an associative array `key => value`. The key (`"key"`) becomes a variable (`$key`) in the template.
### Layout
It's possible to create a layout (a model) for a group of pages to make that identical save for the contents.
In a layout it's possible to create a section called **content** that identifies content that can be specified at runtime.
> **Note**: Since only the template has the data passed eventual loops have to be done there.
```php
# index.php
require 'vendor/autoload.php';
use League\Plates\Engine;
$template = new Engine('/path/to/templates');
echo $template->render('template_name', [ "marker" => value, ... ]);
```
```php
# template.php
# set the layout used for this template
<?php $this->layout("layout_name", ["marker" => value, ...]) ?> # pass values to the layout
# section contents
<p> <?= $this->e($marker) ?> </p>
```
```php
# layout.php
<html>
<head>
<title><?= $marker ?></title>
</head>
<body>
<?= $this->section('content')?> # insert the section
</body>
</html>
```
### Escape
It's necessary to verify that the output is in the necessary format.
Plates offers `$this->escape()` or `$this->e()` to validate the output.
In general the output validation allows to prevent [Cross-Site Scripting][owasp-xss] (XSS).
[owasp-xss]: https://owasp.org/www-community/attacks/xss/
### Folders
```php
# index.php
$templates->addFolder("alias", "path/to/template/folder"); # add a template folder
echo $templates->render("folder::template"); # use a template in a specific folder
```
### Insert
It's possible to inject templates in a layout or template. It is done by using the `insert()` function.
```php
# layout.php
<html>
<head>
<title><?=$this->e($title)?></title>
</head>
<body>
<?php $this->insert('template::header') ?> # insert template
<?= $this->section('content')?> # page contents
<?php $this->insert('template::footer') ?> # insert template
</body>
</html>
```
### Sections
It's possible to insert page contest from another template with the `section()` function.
The content to be inserted must be surrounded with by the `start()` and `stop()` functions.
```php
# template.php
<?php $this->start("section_name") ?> # start section
# section contents (HTML)
<?php $this->stop() ?> # stop section
# append to section is existing, create if not
<?php $this->push("section_name") ?>
# section contents (HTML)
<?php $this->end() ?>
```