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php

Re: what happened to that new isset() like language

php.internals

Cris H

22 years ago

Isn't this problem solvable with just a "User Space" function?

<?php

error_reporting(E_ALL);

function ifsetor(&$variable, $alternate = NULL){
if(isset($variable)){
$tmp = $variable;
echo('<p>$variable exists.</p>');
}
else{
$tmp = $alternate;
echo('<p>no $variable here.</p>');
}
return $tmp;
}

// no errors thrown ...

$nonexistent = ifsetor($nonexistent);
ifsetor($randomNonexistent);

if($nonexistent !== NULL)
echo('<p>$nonexistent is NOT NULL</p>');
else
echo('<p>$nonexistent is NULL</p>');

?>

Because, as Derick Rethans mentioned, arguments passed by
reference will not trigger the Undefined (variable | index)
Notice at the point of the function call, and also PHP's C++
style default arguments providing the alternate value, surely
the above code would suffice?

Apologies if I've completely misunderstood (with certainty a
non-zero probability)...

Regards,

Cris





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Sean Coates

22 years ago

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Cris H wrote:
| Isn't this problem solvable with just a "User Space" function?
[snip]
| Because, as Derick Rethans mentioned, arguments passed by
| reference will not trigger the Undefined (variable | index)
| Notice at the point of the function call, and also PHP's C++
| style default arguments providing the alternate value, surely
| the above code would suffice?
|
| Apologies if I've completely misunderstood (with certainty a
| non-zero probability)...
|

I understand that this is not sufficient because of the following
circumstance:

$var = ifsetor($_GET['test'], foo());

foo() is ALWAYS evaluated with the user-space function you wrote. I
understand that we don't want foo() to be called unless it needs to be
returned (ie, we want to be able to short circuit the parameters)?

Now, maybe _I'M_ misunderstanding? (-: I don't have much knowledge of
internals, but is this even POSSIBLE as a function call, and not as an
operator?

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Todd Ruth

22 years ago

That would satisfy some of the requested feature, but try
calling ifsetor($my_array['bad key'], functionWithSideEffects()).
Marcus has repeatedly mentioned that the requested feature is
hard (bordering on impossible) to implement, but in the requested
feature (if I understand it (and it is what I would ask for too :) )),
there would be no error for using a key that isn't in the array,
there would be no side effect of creating a key in the array, and
if the $my_array['bad key'] actually did happen to be non-NULL,
the function with the side effects wouldn't get called.

That would be really handy, especially if it could take a variable
number of arguments.  Using a standard name like coalesce would
be nice.

BTW, I have no weight around here; just thought I could help
clarify, having following this thread with interest...

- Todd

On Fri, 2004-07-09 at 12:07, Cris H wrote:

Cris H

22 years ago

> That would satisfy some of the requested feature, but try
> calling ifsetor($my_array['bad key'],
> functionWithSideEffects()).

That could be circumvented (somewhat hackishly, I concede) by
recoding a new function and passing the second arg as the string
"functionWithSideEffects" and using the dereferencing () trick.

Although, I did indeed overlook the issue of not evaluating the
second arg unnecessarily. Tricky.

To quote from the classics: D'oh!

Regards,

Cris

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