valid.php

<?php defined('SYSPATH') OR die('No direct script access.');

class Valid extends Kohana_Valid {

	public static function slug($str)
	{
		if (preg_match('/^[a-zA-Z0-9_-]+$/D', $str, $matches))
		{
			// Strip multiple dashes and trim an ending or starting dashes
			return ($str === preg_replace('/-{2,}/', '-', trim($matches[0], '-')));
		}
		
		return FALSE;
	}

}