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Re: switch with case 0 [message #182602 is a reply to message #182589]

Sat, 17 August 2013 17:28

Norman Peelman
Messages: 126
Registered: September 2010

Karma:

Senior Member

On 08/17/2013 12:55 AM, Fiver wrote:
> This example
>
> switch ("foo") {
> case 0:
> echo "'foo' is 0\n";
> break;
> default:
> echo "'foo' is not 0\n";
> }
>
> will print: 'foo' is 0.
>
> I know how to avoid the problem, I'm just wondering what kind of
> comparison is used that makes "foo" equal to 0? The manual mentions
> "loose comparison", but this is even looser than usual.
>

Type juggling is done at every CASE statement, consider the following:

switch ("foo") {
case "foo":
echo "'foo' is 'foo'!\n";
//break;
case 0:
echo "'foo' is 0\n";
break;
default:
echo "'foo' is not 0\n";
}

switch ("2bar") {
case "bar":
echo "'bar' is 'bar'!\n";
//break;
case 0:
echo "'bar' is 0\n";
break;
default:
echo "'bar' is not 0\n";
}

> By the way, the original code was meant to validate SORT_* arguments.
> It's a little harder to spot here:
>
> 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");
> }
>
> SORT_REGULAR is 0, so if the input is a string, this will break (literally).
>
>

No, it will just default to SORT_REGULAR if the string type juggling
results in 0.

--
Norman
Registered Linux user #461062
-Have you been to www.php.net yet?-

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[Message index]

		switch with case 0 By: Fiver on Sat, 17 August 2013 04:55
		Re: switch with case 0 By: J.O. Aho on Sat, 17 August 2013 06:35
		Re: switch with case 0 By: The Natural Philosoph on Sat, 17 August 2013 07:29
		Re: switch with case 0 By: Luuk on Sat, 17 August 2013 07:51
		Re: switch with case 0 By: Thomas Mlynarczyk on Sat, 17 August 2013 11:16
		Re: switch with case 0 By: Peter H. Coffin on Sat, 17 August 2013 15:56
		Re: switch with case 0 By: The Natural Philosoph on Sat, 17 August 2013 16:45
		Re: switch with case 0 By: Tim Streater on Sat, 17 August 2013 17:58
		Re: switch with case 0 By: The Natural Philosoph on Sat, 17 August 2013 18:39
		Re: switch with case 0 By: Thomas Mlynarczyk on Sat, 17 August 2013 19:36
		Re: switch with case 0 By: Thomas Mlynarczyk on Sat, 17 August 2013 20:14
		Re: switch with case 0 By: Norman Peelman on Sat, 17 August 2013 17:56
		Re: switch with case 0 By: Thomas Mlynarczyk on Sat, 17 August 2013 19:55
		Re: switch with case 0 By: The Natural Philosoph on Sat, 17 August 2013 20:04
		Re: switch with case 0 By: Thomas Mlynarczyk on Sat, 17 August 2013 20:32
		Re: switch with case 0 By: Richard Yates on Sat, 17 August 2013 22:20
		Re: switch with case 0 By: Fiver on Sat, 17 August 2013 20:37
		Re: switch with case 0 By: Norman Peelman on Sat, 17 August 2013 23:26
		Re: switch with case 0 By: The Natural Philosoph on Sun, 18 August 2013 11:54
		Re: switch with case 0 By: Norman Peelman on Sun, 18 August 2013 00:23
		Re: switch with case 0 By: Thomas Mlynarczyk on Sun, 18 August 2013 13:22
		Re: switch with case 0 By: Norman Peelman on Sun, 18 August 2013 15:20
		Re: switch with case 0 By: Thomas Mlynarczyk on Sun, 18 August 2013 16:28
		Re: switch with case 0 By: Norman Peelman on Sun, 18 August 2013 19:16
		Re: switch with case 0 By: Norman Peelman on Sun, 18 August 2013 22:04
		Re: switch with case 0 By: Thomas Mlynarczyk on Sun, 18 August 2013 22:17
		Re: switch with case 0 By: Thomas Mlynarczyk on Sun, 18 August 2013 22:13
		Re: switch with case 0 By: The Natural Philosoph on Sun, 18 August 2013 23:35
		Re: switch with case 0 By: Norman Peelman on Mon, 19 August 2013 10:30
		Re: switch with case 0 By: Norman Peelman on Mon, 19 August 2013 02:13
		Re: switch with case 0 By: Thomas Mlynarczyk on Mon, 19 August 2013 17:55
		Re: switch with case 0 By: Thomas 'PointedEars' on Mon, 19 August 2013 08:18
		Re: switch with case 0 By: Thomas Mlynarczyk on Mon, 19 August 2013 17:39
		Re: switch with case 0 By: Fiver on Sat, 17 August 2013 14:15
		Re: switch with case 0 By: Norman Peelman on Sat, 17 August 2013 17:28

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