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Date: Tue, 25 Mar 2025 20:11:28 +0000
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Subject: Re: [PHP-DEV] Feedback for nullc Idea
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From: imsop.php@rwec.co.uk ("Rowan Tommins [IMSoP]")



On 25 March 2025 16:42:45 GMT, Robert Chapin <php@miqrogroove=2Ecom> wrote=
:
>On 3/25/2025 4:45 AM, Rowan Tommins [IMSoP] wrote:

>> The implied default in the first is 'off', but in the second it's 'on'=
=2E
>I thought the implied default was null=2E


By "implied", I'm talking about the observed behaviour: if you give it nul=
l, does it *act the same as* when you give it 'off', or when you give it 'o=
n'?



>>> A different example could be if (coalesce($_POST['tick']) > 10) return=
;
>> In this case, the implied default is 0=2E
>
>I thought the implied default was null=2E=C2=A0


In this case it's more than implied, the engine is literally converting th=
e value to zero=2E

The logical answer to the question "is null greater than ten?" is "null", =
as used by SQL=2E e=2Eg=2E=20

- "I don't know how many apples are in the box=2E" (set num_apples=3Dnull)
 - "Are there more than ten apples in the box?" (query: num_apples>10)
- "I don't know=2E" (result: null)

The reason you don't get that answer in PHP is that it looks at the contex=
t and "type juggles" the null to an integer, and gives you the answer to "i=
s zero greater than ten?" instead=2E

(In this specific case, you can't observe the difference, because null wou=
ld itself be juggled to false by the if statement; but substitute "less tha=
n ten", and you get true in PHP, still null in SQL=2E)


Using coalesce($foo) in this example means the reader has to remember or g=
uess the type juggling rules to know that it's equivalent to (int)($foo ?? =
null), and that (int)null will give 0=2E

Writing coalesce($foo, 0) or ($foo ?? 0) is a small cost when writing the =
code to save cost every time anyone reads it=2E


Rowan Tommins
[IMSoP]