public static function toVariable($input)
    {
        // Remove dashes and underscores, then convert to camel case.
        $input = self::toSpaceSeparated($input);
        $input = self::toCamelCase($input);

        // Remove leading digits.
        $input = preg_replace('#^[0-9]+.*$#', '', $input);

        // Lowercase the first character.
        $first = substr($input, 0, 1);
        $first = strtolower($first);

        // Replace the first character with the lowercase character.
        $input = substr_replace($input, $first, 0, 1);

        return $input;
    }