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__toString() with strval() and settype()

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Adam Maccabee Trachtenberg

22 years ago

Question:

Given an object, $obj, should strval($obj) and settype($obj, 'string')
return $obj->__toString() if it exists?

They currently do not, but (string) $obj does.

Are these three operations supposed to be identical, but with
different syntax? Or are there other differences among them?

-adam

--
adam@trachtenberg.com
author of o'reilly's php cookbook
avoid the holiday rush, buy your copy today!

Marcus Börger

22 years ago

Hello Adam,

Thursday, January 15, 2004, 7:04:09 PM, you wrote:

> Question:

> Given an object, $obj, should strval($obj) and settype($obj, 'string')
> return $obj->__toString() if it exists?

> They currently do not, but (string) $obj does.

> Are these three operations supposed to be identical, but with
> different syntax? Or are there other differences among them?

Looking at the docs i found this:
Converting to string
You can convert a value to a string using the (string) cast, or the
strval() function. String conversion is automatically done in the scope
of an expression for you where a string is needed. This happens when
you use the echo() or print() functions, or when you compare a variable
value to a string. Reading the manual sections on Types and Type Juggling
will make the following clearer. See also settype().

That means strval($x) is equal to (string)$x.

Looking at settype() i found this:
bool settype ( mixed var, string type)
Set the type of variable var to type.
[...]
See also gettype(), type-casting and type-juggling.

That does not sound like typecasting but it dosn't sound like no
typecasting being involved too. In other words it is unclear.

Looking at TypeJuggling i found:
If you wish to force a variable to be evaluated as a certain type, see
the section on Type casting. If you wish to change the type of a variable,
see settype().


This sounds more like no typecasting but like a string representation. Which
could be result of __toString() as well as a text like 'object of type ...'
or somthing similar.

So i'd go for strval() calling __tostring() and hearing some other meanings
on settype().

--
Best regards,
Marcus                            mailto:helly@php.net

Adam Maccabee Trachtenberg

22 years ago

On Thu, 15 Jan 2004, Marcus Boerger wrote:

Marcus --

> Thursday, January 15, 2004, 7:04:09 PM, you wrote:
>

> > Given an object, $obj, should strval($obj) and settype($obj, 'string')
> > return $obj->__toString() if it exists?
>
> > They currently do not, but (string) $obj does.
>
> > Are these three operations supposed to be identical, but with
> > different syntax? Or are there other differences among them?
>
> Looking at the docs i found this:
> Converting to string
> You can convert a value to a string using the (string) cast, or the
> strval() function. String conversion is automatically done in the scope
> of an expression for you where a string is needed. This happens when
> you use the echo() or print() functions, or when you compare a variable
> value to a string. Reading the manual sections on Types and Type Juggling
> will make the following clearer. See also settype().
>
> That means strval($x) is equal to (string)$x.

That's how I believe it. I see (string) as the way people who know C
cast variables in PHP and strval() as the way non-C programmers cast
stuff. :)

Later on down on that page, it stays that you can't take a strval() of
an object, but I think that's only because before __toString() there
was no meaningful way to handle this.

> Looking at settype() i found this:
> bool settype ( mixed var, string type)
> Set the type of variable var to type.
> [...]
> See also gettype(), type-casting and type-juggling.
>
> That does not sound like typecasting but it dosn't sound like no
> typecasting being involved too. In other words it is unclear.

I had always considered settype() to be a generic version of strval(),
intval(), etc. But maybe it's not.

> So i'd go for strval() calling __tostring() and hearing some other meanings
> on settype().

I would like it if strval() called __toString() and I think it also
makes sense for settype() to work this way, but maybe it would be good
to hear from others, in particular maybe the someone who added these
functions?

-adam

--
adam@trachtenberg.com
author of o'reilly's php cookbook
avoid the holiday rush, buy your copy today!

Adam Maccabee Trachtenberg

22 years ago

Anyone else care to chime in here? If we're really moving to RC1, I
think it makes sense to lock down as many language-level features as
soon as possible.

-adam

On Thu, 15 Jan 2004, Adam Maccabee Trachtenberg wrote:

> On Thu, 15 Jan 2004, Marcus Boerger wrote:
>
> Marcus --
>
> > Thursday, January 15, 2004, 7:04:09 PM, you wrote:
> >
>
> > > Given an object, $obj, should strval($obj) and settype($obj, 'string')
> > > return $obj->__toString() if it exists?
> >
> > > They currently do not, but (string) $obj does.
> >
> > > Are these three operations supposed to be identical, but with
> > > different syntax? Or are there other differences among them?
> >
> > Looking at the docs i found this:
> > Converting to string
> > You can convert a value to a string using the (string) cast, or the
> > strval() function. String conversion is automatically done in the scope
> > of an expression for you where a string is needed. This happens when
> > you use the echo() or print() functions, or when you compare a variable
> > value to a string. Reading the manual sections on Types and Type Juggling
> > will make the following clearer. See also settype().
> >
> > That means strval($x) is equal to (string)$x.
>
> That's how I believe it. I see (string) as the way people who know C
> cast variables in PHP and strval() as the way non-C programmers cast
> stuff. :)
>
> Later on down on that page, it stays that you can't take a strval() of
> an object, but I think that's only because before __toString() there
> was no meaningful way to handle this.
>
> > Looking at settype() i found this:
> > bool settype ( mixed var, string type)
> > Set the type of variable var to type.
> > [...]
> > See also gettype(), type-casting and type-juggling.
> >
> > That does not sound like typecasting but it dosn't sound like no
> > typecasting being involved too. In other words it is unclear.
>
> I had always considered settype() to be a generic version of strval(),
> intval(), etc. But maybe it's not.
>
> > So i'd go for strval() calling __tostring() and hearing some other meanings
> > on settype().
>
> I would like it if strval() called __toString() and I think it also
> makes sense for settype() to work this way, but maybe it would be good
> to hear from others, in particular maybe the someone who added these
> functions?
>
> -adam
>
>

--
adam@trachtenberg.com
author of o'reilly's php cookbook
avoid the holiday rush, buy your copy today!

Christian Schneider

22 years ago

Adam Maccabee Trachtenberg wrote:

> Anyone else care to chime in here? If we're really moving to RC1, I

So to summarize that'd be
echo, print, (string), strval() and settype()
using __toString(), right? Sounds +1 to me.

Right now strval() and settype() don't call __toString() but exit() does.

- Chris

Sterling Hughes

22 years ago

> Adam Maccabee Trachtenberg wrote:
> >Anyone else care to chime in here? If we're really moving to RC1, I
>
> So to summarize that'd be
> echo, print, (string), strval() and settype()
> using __toString(), right? Sounds +1 to me.
>

settype() is a tricky one - i think it should fail for objects, as it
could cause destruction of the underlying object, as we don't have
magic (in the perl internals meaning of the world).

-sterling

--
"Reductionists like to take things apart.  The rest of us are
just trying to get it together."
- Larry Wall, Programming Perl, 3rd Edition

Adam Maccabee Trachtenberg

22 years ago

On Fri, 16 Jan 2004, Sterling Hughes wrote:

> > Adam Maccabee Trachtenberg wrote:
> > >Anyone else care to chime in here? If we're really moving to RC1, I
> >
> > So to summarize that'd be
> > echo, print, (string), strval() and settype()
> > using __toString(), right? Sounds +1 to me.
> >
>
> settype() is a tricky one - i think it should fail for objects, as it
> could cause destruction of the underlying object, as we don't have
> magic (in the perl internals meaning of the world).

Ah right. settype() modifies the original object instead of returning
a cast version of the object. Yea, settype() should probably fail for
objects.

So, it's:

echo, print, (string), strval(), "$obj", and printf("%s", $obj) (plus
printf() variants).

That's my complete list. AFAIK, everything but strval() works right
now. We just need to fix that function.

Also, I don't know why exit() would call __toString(). That doesn't
make sense to me.

-adam

--
adam@trachtenberg.com
author of o'reilly's php cookbook
avoid the holiday rush, buy your copy today!