Legal to pass reference to declared global as default function argument?

[World Wide Weird]

I have a function that requires as arguments a reference to an array and a reference to a scalar variable. This function passes those arguments to another function, which supplies them to a callback function when it gets executed at a later time, e.g., via call_user_func_args. In some cases, the callback may not require an array of arguments or return a value. Therefore, I want to provide an empty array and a null scalar as default arguments. My question is, is it legal to use a variable's name as a default argument in the function's declaration, as shown in this code?

  $empty_array = array();
  $null_output = null;

  function add_idle($callback,&$args = $empty_array,&$ret = $null_output) {
   try {
    $handle = rand_str(16);
    $idle = IdleTaskList::getInstance();
    $idle->addTask($handle,$callback,&$args,&$ret);
    return $handle;
   }
   catch (Exception $e) {
    alert($e->getMessage());
    return false;
   }
  } // add_idle 

[oddz]

no

You also need to supply those referenced arguments. References must be supplied in that context.

There may exists some 5.3 voodoo to get that to work, but as far as I know it's not legal.

[World Wide Weird]

How would you do it? Would it be best to leave those arguments out of the signature and use func_num_args and func_get_args in the function to decide whether anything has been passed? Or would this work?

function add_idle($callback,&$args = array(),&$ret = null) {
...
} 

[oddz]

That will work apparently.

func_get_args() doesn't return references regardless if they are specified as such in the parameters. So I don't think that would work for you if you need references.

[World Wide Weird]

I'll do some tests and see what happens. Thanks!