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Date: Thu, 01 Dec 2005 15:59:12 +0100
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To: Ron Korving <r.korving@xit.nl>
Cc: internals@lists.php.net
References: <F285517D-8EEB-40FB-A069-30E7B315E560@intuitivefuture.com> <374c2968dd7f3d13c696037ef850256f@gravitonic.com> <2D.57.14828.3453E834@pb1.pair.com> <23.98.14828.81AAE834@pb1.pair.com>
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Subject: Re: [PHP-DEV] Named arguments revisited
From: cschneid@cschneid.com (Christian Schneider)

Ron Korving wrote:
> Named parameter example:

Your example misses the main advantage of named parameters IMHO: Sets of 
parameters you don't want to or can't explicitely list because they are 
not know yet.

>   function adduser($params)
>   {
>     if (!is_array($params)) throw new Exception('No named parameters');
>     if (!isset($params['username'])) throw new Exception('Missing parameter: 
> username');
>     if (!isset($params['password'])) throw new Exception('Missing parameter: 
> username');
>     if (!isset($params['superuser'])) $params['superuser'] = false;
> 
>     // now do some stuff with $params
>   }
> 
>   adduser(array('username' => 'root', 'password' => 'abcdefg', 'superuser' 
> => true));

This is not how we use named parameters at all. If you have a finite set 
of fixed parameters then positional parameters are working just fine.

One of the main advantages lies in a catch-all parameter which gets all 
unassignable parameters. While this opens the door for typos even a 
whips'n'chains language like Python added this feature because it is 
just too useful to omit if you have named parameters :-)

Our use case is something along the lines of (not the actual code, so 
don't comment on anything specific here ;-)):

function tag($name, $p = array())
{
	foreach ($p as $key => $value)
	{
		if (is_int($key))
			$content .= $value;
		else
			$attributes .= " $key='$value'";
	}

	return "<$name$attributes>$content</$name>";
}

function a($p = array())
{
	return tag("a", $p);
}

...

echo a(array('href' => $url, 'title' => $title));
or with our patch to make array() obsolete
echo a('href' => $url, 'title' => $title);

Now something like
echo a(href: $url, title: $title, 'non-identifier-chars': 42);
would be even neater, agreed ;-)

- Chris