use MatthiasMullie\Minify;

$sourcePath = '/path/to/source/css/file.css';
$minifier = new Minify($file);

// we can even add another file, they'll then be joined in 1 output file
$sourcePath2 = '/path/to/second/source/css/file.css';
$minifier->add($sourcePath2);

// or we can just add plain CSS
$css = 'body { color: #000000; }';
$minifier->add($css);

// save minified file to disk
$minifiedPath = '/path/to/minified/css/file.css';
$minifier->minify($minifiedPath);

// or just output the content
echo $minifier->minify();

// just look at the CSS example; it's exactly the same, but with JS files :)

Available methods, for both CSS & JS minifier, are:

The object constructor accepts 0, 1 or multiple paths of files, or even complete CSS/JS content, that should be minified. All CSS/JS passed along, will be combined into 1 minified file.

use MatthiasMullie\Minify;
$minifier = new Minify\JS($path1, $path2);

This is roughly equivalent to the constructor.

$minifier->add($path3);
$minifier->add($js);

This will minify the files' content, save the result to $path and return the resulting content. If the $path parameter is false, the result will not be written anywhere.

CAUTION: If you have CSS with relative paths (to imports, images, ...), you should always specify a target path! Then those relative paths will be adjusted in accordance with the new path.

$minifier->minify('/target/path.js');

Simply add a dependency on matthiasmullie/minify to your project's composer.json file if you use Composer to manage the dependencies of your project:

{
    "require": {
        "matthiasmullie/minify": "1.3.*"
    }
}

Although it's recommended to use Composer, you can actually include these files anyway you want.

Minify is MIT licensed.