| Re: switch with case 0 [message #182624 is a reply to message #182623] |
Sun, 18 August 2013 19:16   |
Norman Peelman
Messages: 126
Registered: September 2010
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Senior Member |
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On 08/18/2013 12:28 PM, Thomas Mlynarczyk wrote:
> Norman Peelman schrieb:
>
>> PHP started *before* the big validation era...
>
> This may be true, but does that mean we should not validate in PHP? ;-)
>
By all means no...
>> PHP doesn't just randomly decide to type juggle, it does so in
>> context. If you want a string "42", you have it. PHP won't do anything
>> to it until you try to do some math with it (or explicitly ask it to
>> do so.)
>
> Well, unfortunately, <, <=, >, >= and switch give you no possibility to
> prevent unwanted string->int casts. For equality checks, you can use ===
> and !==, but there are no corresponding operators for <, > etc. And
> that's the problem.
>
$mode = "fop";
echo (($mode === "$mode") AND ($mode <= "foo")) ? "True\n" : "False\n";
>>> Trying to convert "foo" to a number doesn't make sense. It only makes
>>> sense when the string contains the representation of a number.
>>
>> Thomas, methinks you've decided to be dense... PHP has to *look* at
>> the string to determine that.
>
> Methinks differently, but... Of course, PHP has to look. Just looking is
> okay. Messing up is not. But if PHP never tried to look at the string by
> itself -- only when being told to -- things would be much better.
>
When you are comparing things, you are asking PHP to look at them...
>>> That said, if there happened to be a defined constant foo = 42, then
>>> (int)
>>> "foo" could reasonably result in int(42). But in any case, a conversion
>
>> There is no constant "foo". If created, it would be foo. So, no
>> (int)"foo" should not result in a constant foo value. constant("foo")
>> does that just fine.
>
> Oh come on, my English is certainly not perfect, but please -- just a
> little effort trying to understand what I say...?
I don't believe I misunderstood at all... (int)"???" could end up
matching any CONSTANT by accident. Talk about getting unknown
quantities... and your English is just fine. :)
> Again:
> Suppose you have a string "foo" and your task is to convert it to an
> integer. Normally, you'd think there's no reasonable way to do that. But
> if there happened to be a constant foo = 42 defined, it would seem
> reasonable to assume that the string "foo" might refer to that constant
> and therefore convert "foo" to 42. No, I'm not talking about what PHP
> *is* currently doing in such a situation, I'm talking about how a
> computer language should be designed to behave in such a situation.
>
>> PHP type juggles when you ask it to do so (right/wrong/mistake). If
>> it did it implicitly then it would happen before you ever got to the
>> data.
>
> With "foo" < 42, PHP will convert "foo" to 0 and then "do" 0 < 42.
> That's what I call implicit conversion and please correct me if my usage
> of that word happens to be wrong. Explicit would be (int) "foo" < 42.
>
>> "foo" + 2 = 2
>> NULL + 2 = 2
>
> It boils down to this: "foo" + 2 doesn't mean anything. In order to mean
> something, both operands must be of the same type. So, either
>
> "foo" + (string) 2 = "foo" + "2" = "foo2"
>
> as other languages would handle this, or
To me that's the same problem in reverse. + is math, . is
concatination. + needs/wants numbers, . needs/wants strings. You don't
ADD strings, you JOIN/CONCATINATE them.
>
> (int) "foo" + 2 = ??? + 2 = ???
>
= 0 + 2 = 2
"foo" . 2 = "foo2"
> or throw an exception to complain about incompatible operands.
>
> If (int) $somevar yields 0 with $somevar = "foo", then I have no way of
> knowing whether the 0 is the "legitimate" result of the cast or whether
> it just means "couldn't cast that to a number, giving you back 0
> instead". But if in case of failure `null` is returned, I can look at
> the result of (int) $somevar and if it's `null` (and not an integer) I
> know the cast failed and I can react accordingly.
>
Ok Thomas, lets think this through. If a string $somevar contains a
number, you get cast that number. If the cast results in 0 because
$somevar either does not contain a number or contains "0", does it
matter? If 0 is not an acceptable result, you the programmer should more
than likely be coding for that anyway.
> Greetings,
> Thomas
>
--
Norman
Registered Linux user #461062
-Have you been to www.php.net yet?-
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