Twig/doc/intro.rst

Introduction
============

This is the documentation for Twig, the flexible, fast, and secure template
engine for PHP.

If you have any exposure to other text-based template languages, such as
Smarty, Django, or Jinja, you should feel right at home with Twig. It's both
designer and developer friendly by sticking to PHP's principles and adding
functionality useful for templating environments.

The key-features are...

* *Fast*: Twig compiles templates down to plain optimized PHP code. The
  overhead compared to regular PHP code was reduced to the very minimum.

* *Secure*: Twig has a sandbox mode to evaluate untrusted template code. This
  allows Twig to be used as a template language for applications where users
  may modify the template design.

* *Flexible*: Twig is powered by a flexible lexer and parser. This allows the
  developer to define its own custom tags and filters, and create its own DSL.

Prerequisites
-------------

Twig needs at least **PHP 5.2.4** to run.

Installation
------------

You have multiple ways to install Twig.

Installing via Composer (recommended)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

1. Install composer in your project:

.. code-block:: bash

    curl -s http://getcomposer.org/installer | php

2. Create a ``composer.json`` file in your project root:

.. code-block:: javascript

    {
        "require": {
            "twig/twig": "1.*"
        }
    }

3. Install via composer

.. code-block:: bash

    php composer.phar install

.. note::
    If you want to learn more about Composer, the ``composer.json`` file syntax
    and its usage, you can read the `online documentation`_.

Installing from the tarball release
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

1. Download the most recent tarball from the `download page`_
2. Unpack the tarball
3. Move the files somewhere in your project

Installing the development version
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

1. Install Git
2. ``git clone git://github.com/fabpot/Twig.git``

Installing the PEAR package
~~~~~~~~~~~~~~~~~~~~~~~~~~~

1. Install PEAR
2. ``pear channel-discover pear.twig-project.org``
3. ``pear install twig/Twig`` (or ``pear install twig/Twig-beta``)

Installing the C extension
~~~~~~~~~~~~~~~~~~~~~~~~~~

.. versionadded:: 1.4
    The C extension was added in Twig 1.4.

Twig comes with a C extension that enhances the performance of the Twig
runtime engine.

You can install it via PEAR:

1. Install PEAR
2. ``pear channel-discover pear.twig-project.org``
3. ``pear install twig/CTwig`` (or ``pear install twig/CTwig-beta``)

Or manually like any other PHP extension:

.. code-block:: bash

    $ cd ext/twig
    $ phpize
    $ ./configure
    $ make
    $ make install

For Windows:

1. Setup the build environment following the `PHP documentation`_;
2. Use the ``configure --disable-all --enable-cli --enable-twig=shared``
command instead of step 14;
3. ``nmake``;
4. Copy the
``C:\php-sdk\phpdev\vcXX\x86\php-source-directory\Release_TS\php_twig.dll``
file to your PHP setup.

.. tip::

    For Windows ZendServer, TS is not enabled as mentionned in `Zend Server
    FAQ`_.

    You have to use `configure --disable-all --disable-zts --enable-cli
    --enable-twig=shared` to be able to build the twig C extension for
    ZendServer.

    The built DLL will be available in
    C:\php-sdk\phpdev\vcXX\x86\php-source-directory\Release

Finally, enable the extension in your ``php.ini`` configuration file:

.. code-block:: ini

    extension=twig.so #For Unix systems
    extension=php_twig.dll #For Windows systems

And from now on, Twig will automatically compile your templates to take
advantage of the C extension. Note that this extension does not replace the
PHP code but only provides an optimized version of the
``Twig_Template::getAttribute()`` method.

Basic API Usage
---------------

This section gives you a brief introduction to the PHP API for Twig.

The first step to use Twig is to register its autoloader::

    require_once '/path/to/lib/Twig/Autoloader.php';
    Twig_Autoloader::register();

Replace the ``/path/to/lib/`` path with the path you used for Twig
installation.

If you have installed Twig via Composer you can take advantage of Composer's
autoload mechanism by replacing the previous snippet for::

    require_once '/path/to/vendor/autoload.php';

.. note::

    Twig follows the PEAR convention names for its classes, which means you
    can easily integrate Twig classes loading in your own autoloader.

.. code-block:: php

    $loader = new Twig_Loader_String();
    $twig = new Twig_Environment($loader);

    echo $twig->render('Hello {{ name }}!', array('name' => 'Fabien'));

Twig uses a loader (``Twig_Loader_String``) to locate templates, and an
environment (``Twig_Environment``) to store the configuration.

The ``render()`` method loads the template passed as a first argument and
renders it with the variables passed as a second argument.

As templates are generally stored on the filesystem, Twig also comes with a
filesystem loader::

    $loader = new Twig_Loader_Filesystem('/path/to/templates');
    $twig = new Twig_Environment($loader, array(
        'cache' => '/path/to/compilation_cache',
    ));

    echo $twig->render('index.html', array('name' => 'Fabien'));

.. _`download page`: https://github.com/fabpot/Twig/tags
.. _`online documentation`: http://getcomposer.org/doc
.. _`PHP documentation`: https://wiki.php.net/internals/windows/stepbystepbuild
.. _`Zend Server FAQ`: http://www.zend.com/en/products/server/faq#faqD6