anchor.diff:  -spec init() -> [ephp_func:php_function()].
   
   init() -> [
  -    strlen, ord, implode, join
  +    strlen, ord, chr, implode, join
   ]. 
   
   -spec strlen(Context :: context(), String :: var_value()) -> integer().
  
positive.code:     init/0,
      strlen/2,
      ord/2,
      implode/2,
      implode/3,
      join/2,
  
negative.code: 
  ord(_Context, _Var) ->
      %% TODO: Warning: ord() expects parameter 1 to be string
      null.
  
  -spec chr(Context :: context(), Integer :: var_value()) -> binary().
  
  chr(_Context, {_,C}) when is_integer(C) ->
      <<C:8/integer>>;
  
  chr(_Context, _Var) ->
      null.
  
  -spec implode(Context :: context(), Glue :: var_value(), Pieces :: var_value()) -> binary().
  