| Re: switch with case 0 [message #182606 is a reply to message #182593] |
Sat, 17 August 2013 17:56   |
Norman Peelman
Messages: 126
Registered: September 2010
Karma:
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Senior Member |
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On 08/17/2013 07:16 AM, Thomas Mlynarczyk wrote:
> J.O. Aho schrieb:
>
>> PHP will make a type casting and try to make the "foo" to a integer
>
> And that's precisely what PHP shouldn't do. Cast an integer to a string?
> Yes, no problem, since this can be done without loss of information. But
> the other way round, especially if the string is obviously not
> representing a numeric value? That's just plain stupid.
>
That's why it says "foo" = 0. Now is "foo" really 0, no - but it sure
isn't greater than 0. PHP looks at the string in question one character
at a time and builds a number until a non-numeric character is reached
(in a nutshell):
"foo" = 0
"foo2you" = 0
"2fooyou" = 2
"250fooyou" = 250
"250.0fooyou" = 250.0
The (basic) premise is a string can only result in a number if it
starts with a number, otherwise not. If you want to know why "foo" = 0
then, it's the same as doing math with NULL. NULL <> 0 but acts like it
in computations:
2 * "2fooyou" = 4
> PHP should never, never, never try to parse out anything from a string
> *unless* explicitly told to do so. And throw an error or return `null`
> in situations like `(int) "foo"`.
An empty string "" = 0, "foo" does not lead with any *numbers* so
therefor is = 0. Saying (int) "foo" = NULL is like saying "foo" isn't there.
>
>> PHP don't care so much about data types so it internally casts it just
>> to make it easy for those who ain't so good at programming.
>
> Easy?!? No it doesn't. On the contrary. A "noob" programmer could write
> a piece of code like the OPs first example (switch ("foo") ... case 0
> ....) and rightfully assume it "to work", because in what strange
> parallel universe "foo" could possibly equal 0? Even disregarding the
> fact that they are of different types. "foo" == 0? WTF?!?
>
>>> switch ($mode) {
>>> case SORT_ASC:
>>> case SORT_DESC:
>>> case SORT_REGULAR:
>>> case SORT_NUMERIC:
>>> case SORT_STRING:
>>> case SORT_LOCALE_STRING:
>>> case SORT_NATURAL:
>>> case SORT_FLAG_CASE:
>>> break;
>>> default:
>>> throw new \InvalidArgumentException("invalid sort mode: $mode");
>>> }
>
>> Sounds like you are trusting user input
>
> No he isn't, as the above code clearly shows. It would work perfectly
> well in any normal programming language (although, personally, I would
> have used in_array() instead of switch).
>
You are assuming $mode is never a string for one. For two, type
juggling is done at the CASE statement, not the SWITCH statement.
--
Norman
Registered Linux user #461062
-Have you been to www.php.net yet?-
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