leafo/lessphp — pull request #400 by Handfeger (2013-03-22 11:46:50+00:00)
Title: Using square brackets instead of curly brackets to access string content

Accessing Strings via Curly brackets will be deprecated in PHP6
http://php.net/manual/de/language.types.string.php#example-58 (above this example)

also i don't think it is as readable as brackets