Re: [PHP] optional object arguments to a function

Op 2/13/10 8:05 AM, Michael A. Peters schreef:
> I've started working on a class using DOMDocument to assemble MathML in
> php. The class, assuming I actually succeed, will eventually be used for
> parsing LaTeX math equations to MathML without the need to have TeX
> installed. I probably won't be able to support all the possibilities for
> equations that LaTeX does w/o a TeX install (and definitely not user
> defined macros) but I suspect I can (hopefully) cover most of the common
> stuff.
> 
> One thing I don't know how to do, though, is write a function where
> arguments are optional object.
> 
> IE for a function to generate an integral, the limits are optional but
> if specified must be an object (since they may be an equation
> themselves). I want the default to be some kind of a null object so I
> know to do nothing with it if it is null.
> 
> With string/integer you just do
> 
> function foo($a='',$b='',$c=false) {
>   }
> 
> How do I specify a default null object, or otherwise make the argument
> argument optional?

this first one doesn't work:

<?

class Foo
{
	function dobar(stdObject $o = null) { /* ... */ }
}

$e = new Foo;
$f = new Foo;

$f->dobar();			// works
$f->dobar($e);			// catchable fatal
$f->dobar((object)array());	// catchable fatal - check the error msg!?!?

?>

... but if you're able/willing to specify a user defined class then you
have this option:

<?php

class Bar {}

class Foo
{
	function dobar(Bar $o = null) { /* ... */ }
}

$b = new Bar;
$f = new Foo;

$f->dobar($b);
$f->dobar();

?>

>