Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:88323
Mailing-List: contact internals-help@lists.php.net; run by ezmlm
Received-SPF: pass (pb1.pair.com: domain gmail.com designates 209.85.212.180 as permitted sender)
To: internals@lists.php.net
References: <CAKws9z27kVJ87Ur5Qo+ayYHPeeO=aYKpRHUV4TFBXX2iMcgO2A@mail.gmail.com>
 <E8634CF1-C2B4-4C5A-8DDC-531D9599774B@craigfrancis.co.uk>
 <55F6B911.9080400@gmail.com>
 <96BE7F01-D04B-483B-B1A3-B45CED6DFCDC@craigfrancis.co.uk>
 <55F6F08C.1020506@gmail.com>
 <0BEF6D82-CB5F-49F6-A3A4-3267924A0CDA@thesba.com>
 <55F72CA9.2060301@gmail.com>
 <09369945-76FE-4E08-9C2C-15FB0577AD27@thesba.com>
 <55F752E7.9070801@gmail.com>
 <D062C4F7-B56E-422F-A563-C7C4A16D36B0@thesba.com>
 <55F9B4C7.3050700@gmail.com>
 <440C64A2-4B4F-4AEF-ACE3-F3A6637EBAB6@thesba.com>
 <55F9D704.5050002@lsces.co.uk>
 <FD9ABCC5-E928-4810-AE1A-E1DC7E0FB3D1@gmail.com>
 <55F9EFA2.9020908@lsces.co.uk>
 <0022A1D9-DC37-4F49-B58E-FBED5AF872BA@gmail.com>
 <55F9FAB3.2050100@lsces.co.uk> <55FB19CB.7080707@gmail.com>
 <55FB3117.5040204@lsces.co.uk> <55FB3A60.1040601@gmail.com>
 <55FB4270.7000204@lsces.co.uk> <55FB4969.7080600@gmail.com>
 <55FB5BA6.6050606@lsces.co.uk> <55FBF265.5000502@gmail.com>
 <55FBF7B7.4050603@lsces.co.uk>
Message-ID: <55FC1A77.7090406@gmail.com>
Date: Fri, 18 Sep 2015 15:06:47 +0100
User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101
 Thunderbird/38.2.0
MIME-Version: 1.0
In-Reply-To: <55FBF7B7.4050603@lsces.co.uk>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 7bit
Subject: Re: [PHP-DEV] PHP 7.1 - Address PHPSadness #28?
From: rowan.collins@gmail.com (Rowan Collins)

Lester Caine wrote on 18/09/2015 12:38:
> For SQL data coming from any decent database each variable can either
> have a value in, ( which may be an empty string ) or be NULL. The NUMBER
> of fields returned does not matter, a query returning a single record
> can have a variable

Again, I know what NULLs are, and how they can come about; but you made 
it sound like you could run an SQL query and have the first row having 6 
columns, and the second having 5, which is not something I've ever seen. 
(Substitute "record" or "tuple" for "row", and "fields" for "columns", 
if you prefer.)

The number of fields returned DOES matter, because if the same number of 
fields are returned in every case, then the same variables will be 
defined in every case, and there would be no case where exists() would 
return false. But I guess I'll take your word for it that there's some 
way that the number of fields can vary.


> so the third condition is that rather than a field
> being NULL, it does not exist, so testing for isset() only works for a
> field that 'is set' and empty() only works with an empty value.

Sure, sure, I understand that, really, I do.


> Checking for the field being present but NULL needs is_null() but THAT throws a
> notice for those fields which have not been returned in this particular
> result set.

Your problem is not "is_null() throws notices", because that would lead 
to "can I have a version of is_null() which doesn't throw notices?" to 
which the answer is "yes, use isset()". The null condition is the one 
which you CAN detect with current functions; it's the "not set" 
condition which you can't detect, because neither is_null() nor isset() 
will actually affirm the "present but" bit of your condition. That's not 
is_null()'s fault, it's behaving the same way as the rest of the 
language in assuming every uninitialised variable has a null value.


> We are not talking about the number of states stored IN a variable

OK, maybe your example just wasn't a very good choice then, because 
"Vehicle is not old enough to need MOT" feels very much like a state 
being stored somewhere to me. That it is *represented by* a non-existent 
variable is incidental, all you need is *some way of representing it*.


> The date
> value can be a valid date ( and genealogical date goes back before most
> 'empty' date values ) or NULL indicating no date set OR the variable can
> be missing from the result set. If you add in 'empty' one might say we
> have four distinct states?

A PHP variable can have all sorts of states, because you can take 
advantage of loose typing:

$date = new DateTime();
$date = null;
$date = 'TODAY';
$date = -1;
$date = M_PI;

etc

Those are all readily distinguishable, and don't require any changes to 
the language for you to base your code around them.

Regards,
-- 
Rowan Collins
[IMSoP]