That is, the asset bundle configuration array is saved in `assets-prod.php` for production mode, and
`assets-dev.php` for non-production mode.
Compressing and combining assets
--------------------------------
### Using the `asset` Command <a name="using-asset-command"></a>
To improve application performance you can compress and then combine several CSS or JS files into lesser number of files
therefore reducing number of HTTP requests and overall download size needed to load a web page. Yii provides a console
command that allows you to do both.
Yii provides a console command named `asset` to automate the approach that we just described.
### Preparing configuration
In order to use `asset` command you should prepare a configuration first. A template for it can be generated using
To use this command, you should first create a configuration file to describe what asset bundles should
be combined and how they should be grouped. You can use the `asset/template` sub-command to generate
a template first and then modify it to fit for your needs.
```
yii asset/template /path/to/myapp/config.php
yii asset/template assets.php
```
The template itself looks like the following:
The command generates a file named `assets.php` in the current directory. The content of this file looks like the following:
```php
<?php
...
...
@@ -352,127 +572,29 @@ return [
];
```
In the above keys are `properties` of `AssetController`. `bundles` list contains bundles that should be compressed. These are typically what's used by application.
`targets` contains a list of bundles that define how resulting files will be written. In our case we're writing
everything to `path/to/web` that can be accessed like `http://example.com/` i.e. it is website root directory.
You should modify this file and specify which bundles you plan to combine in the `bundles` option. In the `targets`
option you should specify how the bundles should be divided into groups. You can specify one or multiple groups,
as aforementioned.
> Note: in the console environment some path aliases like '@webroot' and '@web' may not exist,
so corresponding paths inside the configuration should be specified directly.
> Note: Because the alias `@webroot` and `@web` are not available in the console application, you should
explicitly define them in the configuration.
JavaScript files are combined, compressed and written to `js/all-{hash}.js` where {hash} is replaced with the hash of
the resulting file.
`jsCompressor` and `cssCompressor` are console commands or PHP callbacks, which should perform JavaScript and CSS files
compression correspondingly. You should adjust these values according to your environment.
By default Yii relies on [Closure Compiler](https://developers.google.com/closure/compiler/) for JavaScript file compression,
and on [YUI Compressor](https://github.com/yui/yuicompressor/). You should install this utilities manually, if you wish to use them.
### Providing compression tools
The command relies on external compression tools that are not bundled with Yii so you need to provide CSS and JS
compressors which are correspondingly specified via `cssCompressor` and `jsCompression` properties. If compressor is
specified as a string it is treated as a shell command template which should contain two placeholders: `{from}` that
is replaced by source file name and `{to}` that is replaced by output file name. Another way to specify compressor is
to use any valid PHP callback.
The `jsCompressor` and `cssCompressor` options specify the console commands or PHP callbacks for performing
JavaScript and CSS combining/compressing. By default Yii uses [Closure Compiler](https://developers.google.com/closure/compiler/)
for combining JavaScript files and [YUI Compressor](https://github.com/yui/yuicompressor/) for combining CSS files.
You should install tools manually or adjust these options to use your favorite tools.
By default for JavaScript compression Yii tries to use
[Google Closure compiler](https://developers.google.com/closure/compiler/) that is expected to be in a file named
`compiler.jar`.
For CSS compression Yii assumes that [YUI Compressor](https://github.com/yui/yuicompressor/) is looked up in a file
named `yuicompressor.jar`.
With the configuration file, you can run the `asset` command to combine and compress the asset files
and then generate a new asset bundle configuration file `assets-prod.php`:
In order to compress both JavaScript and CSS, you need to download both tools and place them under the directory
containing your `yii` console bootstrap file. You also need to install JRE in order to run these tools.
You may customize the compression commands (e.g. changing the location of the jar files) in the `config.php` file
