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From: "Christoph M. Becker" <cmbecker69@arcor.de>
Newsgroups: comp.lang.php
Subject: Re: problem with double as array index?
Date: Wed, 06 May 2015 22:57:43 +0200
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M. Strobel wrote:

> I stumbled upon this problem when trying to define a trivalent logic:
> 
> Interactive test:
> 
> php > if (! define('triFalse',0))    trigger_error('Error defining!');
> php > if (! define('triMaybe',0.5))  trigger_error('Error defining!');
> php > if (! define('triTrue', 1))    trigger_error('Error defining!');
> php >
> php > $triNotarray = array(triFalse=>triTrue, triMaybe=>triMaybe,
> triTrue=>triFalse);
> php > var_dump($triNotarray);
> array(2) {
>   [0] =>
>   double(0.5)
>   [1] =>
>   int(0)
> }
> 
> Where is my Maybe value?

You're triMaybe is there; triFalse is missing, however.

> I was not aware of this problem (not coding PHP for some time), what is it?

Firstly, a simplification:

  var_dump(array(0 => 'foo', 0.5 =>'foo', 1 => 'foo'));

Explanation: when a float is used as array key, it is cast to int, see
<http://php.net/manual/en/language.types.array.php#language.types.array.syntax>.
 So the second element overwrites the first element.

-- 
Christoph M. Becker