New operator suggestion

Hello,

I would like to suggest a new PHP operator, which in my opinion PHP
needs to become more stricter.
At first, I invited nullish coalescing (??) operator, since it made my
code shorter and easier
to read. However, after some time, I realized that this is not a good
way to go, since it makes
my code much less strict. The nullish coalescing function is what I
need, however what I don't
want in some cases is its error suppression function.

Here is an example I use a lot while generating forms:
<input value="&lt;?=$var->prop1->prop2 ?? ''?>" />

I have ?? operator here, mainly because prop2 can be undefined, but in a
lot of cases I know that
prop1 exists, or at least $var. Issue is, that there is no error
outputted even when $var is
undefined and I missed such errors a lot. In my opinion is not good to
learn people to suppress
whatever error might occur in the whole expression.

Back to the suggestion - I suggest creating a new IFNULL operator, which
will simply test if
expression is null. If not, it returns left-hand part, if yes, it
returns right-hand part.
A suggested token for such operator is "??:" as a mix between "??" and
"?:" tokens. Basically
elvis token "?:" but with strict comparison to null, instead of loose
comparison to false.

With new suggested operator a safe way to write expression above, where
I only expect prop2 to
be undefined would look like this:

$var->prop1?->prop2 ??: '';

Notice, that use of newer operator "?->" really fits here. It clearly
marks, what I expect
to be undefined and "??:" operator just takes the role of converting
possible "null" into and
empty string.

What do you think about this? Is it worth to introduce this new operator
to promote more
strictness of PHP? Is it worth to create an RFC for this? I never did an
RFC yet and has not much
experience with C++, since I am mostly Delphi/PHP/JS developer, but I
might try. Still, I would
appreciate a help from someone willing and experienced in RFC creation.

Thank you in advance for your opinions,
David Kolář

Well, yes, but not exactly.

What I dislike on ?? operator is, that it supress all warnings in the
expression - in my opinion it shares the same
issue as @ operator and why people discourage other to use it - because
it may supress far more errors than you want
to supress. And this is the case with $var->prop1->prop2 - when I expect
just prop2 being undefined, it supresses even
error of undefined $var, which might not be intentional and I miss that
error because of that. So suggested ??: operator
should behave like ??, but without the supression mechanic - just short
hand for
"$x === null ? $x : expr" instead of "isset($x) ? $x : expr".

The 2nd case you wrote is actually even weird to me - I am not sure at
all if PHP should behave like that. Because in
your example, when $var is undefined:

$var->prop1->prop2 ?? ''
does not emit any error, because ?? supresses them

$var?->prop1?->prop2 ?? ''
does emit error - which is weird, since ?-> is still wrapped under ??,
so I am not sure why error shows here.

Anyway what I want is emitting error on undefined $var and undefined
prop1, but NOT undefined prop2, when:
$var->prop1?->prop2 ??: ''

Do you get it? Just a shorthand for this:
$var->prop1?->prop2 === null ? $var->prop1->prop2 : '';

Which any of suggested current solutions can't do.

David

David Kolář wrote on 9/4/21 17:19:

Back to the suggestion - I suggest creating a new IFNULL operator, which
will simply test if
expression is null. If not, it returns left-hand part, if yes, it
returns right-hand part.
This is already what the ?? operator does. For example:
https://3v4l.org/RlDjK

Are you suggesting that it should emit a warning if $var is undefined,
as it does in this case? https://3v4l.org/aZAj0

Cheers,
Ben