rotate_left = function (n, s) {
        var t4 = (n << s) | (n >>> (32 - s));
        return t4;
    }
Gets a SHA1 hash

@param string $input

@return string

@see http://kevin.vanzonneveld.net
  original by: Webtoolkit.info (http://www.webtoolkit.info/)
namespaced by: Michael White (http://getsprink.com)
     input by: Brett Zamir (http://brett-zamir.me)
  improved by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
   depends on: utf8_encode