Combining, Compiling and Minimizing Web Assets with PHP Libraries

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Read the updated version of this page for Symfony 7.1 (the current stable version).

Caution

Starting from Symfony 2.8, Assetic is no longer included by default in the Symfony Standard Edition. Refer to this article to learn how to install and enable Assetic in your Symfony application.

The official Symfony Best Practices recommend to use Assetic to manage web assets, unless you are comfortable with JavaScript-based front-end tools.

Even if those JavaScript-based solutions are the most suitable ones from a technical point of view, using pure PHP alternative libraries can be useful in some scenarios:

  • If you can't install or use npm and the other JavaScript solutions;
  • If you prefer to limit the amount of different technologies used in your applications;
  • If you want to simplify application deployment.

In this article, you'll learn how to combine and minimize CSS and JavaScript files and how to compile Sass files using PHP-only libraries with Assetic.

Installing the Third-Party Compression Libraries

Assetic includes a lot of ready-to-use filters, but it doesn't include their associated libraries. Therefore, before enabling the filters used in this article, you must install two libraries. Open a command console, browse to your project directory and execute the following commands:

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$ composer require leafo/scssphp
$ composer require patchwork/jsqueeze

Organizing your Web Asset Files

This example will include a setup using the Bootstrap CSS framework, jQuery, FontAwesome and some regular CSS and JavaScript application files (called main.css and main.js). The recommended directory structure for this set-up looks like this:

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web/assets/
├── css
│   ├── main.css
│   └── code-highlight.css
├── js
│   ├── bootstrap.js
│   ├── jquery.js
│   └── main.js
└── scss
    ├── bootstrap
    │   ├── _alerts.scss
    │   ├── ...
    │   ├── _variables.scss
    │   ├── _wells.scss
    │   └── mixins
    │       ├── _alerts.scss
    │       ├── ...
    │       └── _vendor-prefixes.scss
    ├── bootstrap.scss
    ├── font-awesome
    │   ├── _animated.scss
    │   ├── ...
    │   └── _variables.scss
    └── font-awesome.scss

Combining and Minimizing CSS Files and Compiling SCSS Files

First, configure a new scssphp Assetic filter:

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# app/config/config.yml
assetic:
    filters:
        scssphp:
            formatter: 'Leafo\ScssPhp\Formatter\Compressed'
        # ...

The value of the formatter option is the fully qualified class name of the formatter used by the filter to produce the compiled CSS file. Using the compressed formatter will minimize the resulting file, regardless of whether the original files are regular CSS files or SCSS files.

Next, update your Twig template to add the {% stylesheets %} tag defined by Assetic:

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{# app/Resources/views/base.html.twig #}
<!DOCTYPE html>
<html>
    <head>
        <!-- ... -->

        {% stylesheets filter="scssphp" output="css/app.css"
            "assets/scss/bootstrap.scss"
            "assets/scss/font-awesome.scss"
            "assets/css/*.css"
        %}
            <link rel="stylesheet" href="{{ asset_url }}"/>
        {% endstylesheets %}

This simple configuration compiles, combines and minifies the SCSS files into a regular CSS file that's put in web/css/app.css. This is the only CSS file which will be served to your visitors.

Combining and Minimizing JavaScript Files

First, configure a new jsqueeze Assetic filter as follows:

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# app/config/config.yml
assetic:
    filters:
        jsqueeze: ~
        # ...

Next, update the code of your Twig template to add the {% javascripts %} tag defined by Assetic:

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<!-- ... -->

    {% javascripts filter="?jsqueeze" output="js/app.js"
        "assets/js/jquery.js"
        "assets/js/bootstrap.js"
        "assets/js/main.js"
    %}
        <script src="{{ asset_url }}"></script>
    {% endjavascripts %}

    </body>
</html>

This simple configuration combines all the JavaScript files, minimizes the contents and saves the output in the web/js/app.js file, which is the one that is served to your visitors.

The leading ? character in the jsqueeze filter name tells Assetic to only apply the filter when not in debug mode. In practice, this means that you'll see unminified files while developing and minimized files in the prod environment.

This work, including the code samples, is licensed under a Creative Commons BY-SA 3.0 license.
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