public static function backSlash($str, $unify = false)
    {
        return self::_slash($str, '\\', false, true, $unify);
    }
public static function backSlash($str, $unify = false)
    {
        return self::_slash($str, '\\', false, true, $unify);
    }
public static function backSlash ( $ str , $ unify = false ) { return self :: _slash ( $ str , '\\' , false , true , $ unify ) ; }
add backslash to the end of the string.

@access public
@param  string  $str    the string to be backslash
@param  boolean $unify  set true to unify all slashes in $str
@return string          the backslashed string
add backslash to the end of the string .