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To: "internals@lists.php.net" <internals@lists.php.net>, "Ben Schmidt"
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Date: Thu, 14 Apr 2011 10:20:01 +0200
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Subject: Re: [PHP-DEV] Implicit isset/isempty check on short-ternary operator
From: olemarkus@olemarkus.org ("Ole Markus With")

On Thu, 14 Apr 2011 02:24:56 +0200, Ben Schmidt  
<mail_ben_schmidt@yahoo.com.au> wrote:

>> I think these shortcuts could be really useful for array elements, but
>> for other variables I am really sceptical and I think they would do
>> more harm than good. Generally I do not really see any reason why a
>> variable should not be 'instanciated' before use.
>>
>> So
>> +1 if this shortcut is implemented to only work for array elements.
>> -1 for any other variable type.
>
> There are two issues here.
>
>     1. Suppression of notice. I agree, it is best done only for array
>     keys. It's not hard to initialise a variable with $var=null at the
>     beginning of a code block to avoid such a notice, and that is the
>     appropriate way to do it for variables.
>
>     2. Offering a shortcut for the common idiom isset($x) ? $x : $y in
>     line with the DRY design principle. A notice would never be emitted
>     here in any case. The problem is that this idiom is still in wide use
>     despite the shortcut ternary operator already provided, because an
>     isset() check is different to a boolean cast.
>
> Some thoughts:
>
>     - The actual intent of 2. is probably $x!==null ? $x : $y i.e. it's
>       not about suppressing notices at all, but about offering a default
>       value, and the idiom quite probably only uses isset() because it
>       predated null in the language.
>

I have never felt the need for a shortcut in these cases. It would be  
interesting to see some code where this would be practical.

>     - If we view 2. in this way, the two problems are independent, and it
>       seems to me it would be best to solve them independently, rather
>       than with a single operator.
>
> So, I suggest:
>
>     1. An array lookup mechanism that suppresses the notice for undefined
>     keys. It would work the same as regular array index lookups except
>     that the notice for undefined keys (and only for undefined keys)
>     would not be generated (it would not just be hidden, but would never
>     be even generated).

This is what I feel PHP is missing. Particularly when it comes to  
multi-dimensional arrays. Because this feature is missing I tend to do  
something like

function generateHash($x, $y, $z)
{
  return "$x::$y::$z";
}

if (isset($a[generateHash($x, $y, $z)]) {
  ...
}

instead of

if (isset($a[$x]) && isset($a[$x][$y]) && isset($a[$x][$y][$z])) {
  ...
}

> Arguing about syntax is then a second step. However, my views on this
> are:
>

I think it best to avoid discussing the actual syntax before agreeing on  
what we really need.

-- 
Ole Markus With
Systems Architect - Sportradar AS
Developer - Gentoo Linux