Re: Is this a PHP bug?

[Ross Honniball <ross@xxxxxxxxxxxxxxxxxxx>]

I had a look at the link and couldn't find the quote you have below, but I am happy to believe you.

Viewed in this context, I guess it does behave correctly and predictably.

I'll have to be more careful with my type mixing in future.

Thanks for your input ... Ross

Paul Menard wrote:
> Well per this PHP page: http://us2.php.net/manual/en/language.operators.comparison.php,
> "If you compare an integer with a string, the string is converted to a number. "
>
> So to follow this regarding your example:
>
> $x = 0; // Numeric zero
> $y = 'Some kind of string';
>
> if (is_null($x)) echo "x is NULL<br>";
> if (is_null($y)) echo "y is NULL<br>";
>
> echo "x is [" . gettype($x) . "]<br>";
> echo "y is [" . gettype($y) . "]<br>";
>
> echo "y as integer=[" . (int)($y) . "]<br>";
>
> if ($x == $y) echo 'they equal using ==';
> if ($x === $y) echo 'they equal using ===';
>
>
> As you might see from the line 'echo "y as integer...' if you cast the string, $y, as an integer
> per the PHP page referenced above the value reported is integer zero. So this is how if can equal
> $x which is already an integer and value zero itself.
>
> No for some of you assumptions philosophies etc.
>
> Many think PHP is a typeless language. This is not accurate. PHP is actually a loosley-typed
> language. This is evident from the ability to assign type to variables. Also in the fact that you
> are allowed to compared variables to each other (at you own risk) even if the types do not match.
> This is very unlike other strong-typed languages like C and C++. 
>
> The designers of the PHP language semantics had to make a choice in how a compare of mixed-typed
> variables would be handled. In my opinion, being a C++ developer in a former life, it is easier to
> convert the string to numeric than the numeric to string for the 'on-the-fly' compare.
>
> I hope this helps your understanding. My suggestion is if you are still of the mind this is a bug
> report it to PHP.
>
> P-  
>
>
> --- Ross Honniball <ross@xxxxxxxxxxxxxxxxxxx> wrote:
>
>
> > I'm yet to be convinced it isn't a bug. I suspect it is a bug that has been around so long that
> > they can't afford to fix it or it may break many applications that for various peculiar reasons
> > rely on it to behave as it does for their code to work.
> >
> > For those who have tried to defend its behaviour, this is my logic.
> >
> > 1. The == operator means, by definition, "don't worry about variable 'type', just compare the
> > values"
> >   (This is probably the single thing I love about PHP more than anything else)
> >
> > 2. If the numeric variable $x is given ANY other numeric value other than zero, 
> >   the logic behaves correctly as you read it
> >
> > So it is irrational for program logic to vary between a zero value and, for aguments sake, a
> > numeric value of 42.
> >
> > Regarding specifically TG's explanation below, I believe he is wrong. If you compare a numeric
> > type and a string type using ==, PHP should convert the number to a string and compare the two
> > from there.
> >
> > Anyway, not expecting any answers to this, just a point of note and a strange quirk to keep at
> > the back of your head when consciously comparing numeric / string variables.
> >
> > Ross
> >
> > tg-php@xxxxxxxxxxxxxxxxxxxxxx wrote:
> >
> > > It's because PHP is trying to convert different var types into a common var type and then
> >
> > compare them when you use ==.  === means compare value AND type so that's why it fails.
> >
> > > Your string, 'Some kind of string' is getting converted down to the lowest common denominator,
> >
> > an int.  Since there are no numbers in the string to grab onto, it gets converted to nothing, an
> > int value of zero.
> >
> > > If you had $x = "0" or if $y had contained numbers at all, it wouldn't have passed.
> > >
> > > But this is why when you use $x.'' it works properly because now you have "0<empty string>",
> >
> > it's been converted to a string value "0".  Good catch on that though, shows good methodical
> > debugging :)
> >
> > > So in the future, either use === or be extra aware of your variable types and make sure you're
> >
> > comparing properly.
> >
> > > Good luck!
> > >
> > > -TG
> > >
> > > = = = Original message = = =
> > >
> > > $x = 0; // Numeric zero
> > > $y = 'Some kind of string';
> > >
> > > if ($x == $y) echo 'they equal using ==';
> > > if ($x === $y) echo 'they equal using ===';
> > >
> > > The above will echo 'they equal using =='.
> > >
> > > The values don't look very equal to me.
> > >
> > > Can anyone explain the logic behind this?
> > >
> > > I'm heading home now but look forward to your explanations tomorrow.
> > >
> > > PS
> > >
> > > Incidently, to 'fix' it so it behaves as it should, you can code:
> > >
> > > if ($x.'' == $y.'') echo 'this will not print and all is good.';
> > >
> > > Regards .. Ross
> > >
> > >
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