PHP listing function arguments with initial values

Question

So I know that you can code for a function's arguments to have a default value if it is not supplied when the function is called like this:

I added an example of how the interface could be implemented:

interface my_interface {

  function my_function();

}

class my_class implements my_interface {

  # because the interface calls for a function with no options an error would occur
  function my_function($arg_one, $arg_two = 'name') {
    ...
  }

}


class another_class implements my_interface {

  # this class would have no errors and complies to the implemented interface
  # it also can have any number of arguments passed to it
  function my_function() {

    list($arg_one, $arg_two, $arg_three) = func_get_args();

    ...

  }

}

However, I like making my functions invoke the func_get_args() method instead so that when using them inside classes I can implement functions from an interface. Is there a way to use the list() function so that I can assign variables a default value or do I need to do it the verbose and ugly way? What I have right now is:

function my_function() {

  list($arg_one, $arg_two) = func_get_args();
  if(is_null($arg_two)) $arg_two = 'name';

  ...

}

What I would like, is something that accomplishes the same thing, but isn't so verbose. Maybe something like this, but of course doesn't flag an error:

function my_function() {

  # If $arg_two is not supplied would its default value remain unchanged?
  # Thus, would calling the next commented line would be my solution?
  # $arg_two = 'name';
  list($arg_one, $arg_two = 'name') = func_get_args();

  ...

}

I'm not sure why you're doing this, what do you mean by "so that when using them inside classes I can implement functions from an interface?". Could you illustrate why does it matter? — elclanrs
– elclanrs, Commented Jul 22, 2013 at 0:13
i made edits to make the understanding a little better @elclanrs — rollingcodes
– rollingcodes, Commented Jul 22, 2013 at 20:53

Oswald · Accepted Answer · 2013-07-22 00:20:51Z

3

You cannot use default values with the list language construct. You can, however, use the modified ternary operator available since PHP 5.3:

function my_function() {
  $arg_one = func_get_arg(0) ?: 'default_one';
  $arg_two = func_get_arg(1) ?: 'name';
  // ...
}

However, beware of implicit type conversions. In my example, my_function(0, array()) behaves the same as my_function('default_one', 'name').

edited Jul 22, 2013 at 0:20

answered Jul 22, 2013 at 0:14

Oswald

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1 Comment

rollingcodes Over a year ago

oh that's clever and looks nice. bummer I can't modify the list function.

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