array( ‘name’ => <theme_name>, ‘custom’ => <dir> );
<dir> can be a string or an array of strings
Every css will be parsed and included on a single output, which will be cached by browser.
The suggestion is to create a PHP file, with the needed definitions and include this file, placing a:
<link href=”<your_file>” type=”text/css” />
In your output to the browser.