Debian Bug report logs - #734129
switch($X){case 'Y':trigger_error("can you believe \$X is NOT Y but Z"); }

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Message #5 received at submit@bugs.debian.org (full text, mbox, reply):

From: jidanni@jidanni.org

To: submit@bugs.debian.org

Subject: switch($X){case 'Y':trigger_error("can you believe \$X is NOT Y but Z"); }

Date: Sat, 04 Jan 2014 09:45:14 +0800

Package: php5-cli
Version: 5.5.7+dfsg-2
Severity: important

$ cat n.php
<?php
$wgSitename='ABJ';
$wgSitename=0;
switch($wgSitename){case 'ABJ':trigger_error("can you believe \$wgSitename is $wgSitename and not ABJ?!",E_USER_WARNING);}
$wgSitename=0;
$wgSitename='ABJ';
switch($wgSitename){case 0:trigger_error("can you believe \$wgSitename is $wgSitename and not 0?!",E_USER_WARNING);}
$ php n.php
PHP Warning:  can you believe $wgSitename is 0 and not ABJ?! in /mnt/usb/cf/n.php on line 4
PHP Warning:  can you believe $wgSitename is ABJ and not 0?! in /mnt/usb/cf/n.php on line 7

What in the world is going on?

Message #10 received at 734129-done@bugs.debian.org (full text, mbox, reply):

From: jidanni@jidanni.org

To: daniel@nadir-seen-fire.com

Cc: mediawiki-l@lists.wikimedia.org, 734129-done@bugs.debian.org

Subject: Re: switch($X){case 'Y':trigger_error("can you believe \$X is NOT Y but Z"); }

Date: Sat, 04 Jan 2014 10:07:16 +0800

OK I see,
http://www.php.net/manual/en/control-structures.switch.php#86911
http://www.php.net/manual/en/control-structures.switch.php#97112
http://www.php.net/manual/en/control-structures.switch.php#84150
How awful. No wonder people write
http://me.veekun.com/blog/2012/04/09/php-a-fractal-of-bad-design/

Message #11 received at 734129-done@bugs.debian.org (full text, mbox, reply):

From: Bob Proulx <bob@proulx.com>

To: 734129-submitter@bugs.debian.org, 734129-done@bugs.debian.org

Subject: Re: Bug#734129: switch($X){case 'Y':trigger_error("can you believe \$X is NOT Y but Z"); }

Date: Fri, 3 Jan 2014 19:10:55 -0700

[Message part 1 (text/plain, inline)]

jidanni@jidanni.org wrote:
> $ cat n.php
> <?php
> $wgSitename='ABJ';
> $wgSitename=0;
> switch($wgSitename){case 'ABJ':trigger_error("can you believe \$wgSitename is $wgSitename and not ABJ?!",E_USER_WARNING);}
> $wgSitename=0;
> $wgSitename='ABJ';
> switch($wgSitename){case 0:trigger_error("can you believe \$wgSitename is $wgSitename and not 0?!",E_USER_WARNING);}
> $ php n.php
> PHP Warning:  can you believe $wgSitename is 0 and not ABJ?! in /mnt/usb/cf/n.php on line 4
> PHP Warning:  can you believe $wgSitename is ABJ and not 0?! in /mnt/usb/cf/n.php on line 7
> 
> What in the world is going on?

You have a bug in your php code.  You are comparing strings and
numbers together.  Never do that.  That is a well known PHP design
choice (and mis-feature).  PHP programmers must understand how types
are automatically converted.  Sure it is a bad design but that is just
the way PHP is.

Specifically PHP switch statements use "==" comparison not "==="
comparison and "==" comparison is poorly designed.

  http://php.net/manual/en/control-structures.switch.php

And also:

  http://docs.php.net/manual/en/language.operators.comparison.php#language.operators.comparison

There is an explicit example of this in that latter reference.

  <?php
  var_dump(0 == "a"); // 0 == 0 -> true
  var_dump("1" == "01"); // 1 == 1 -> true
  var_dump("10" == "1e1"); // 10 == 10 -> true
  var_dump(100 == "1e2"); // 100 == 100 -> true

  switch ("a") {
  case 0:
      echo "0";
      break;
  case "a": // never reached because "a" is already matched with 0
      echo "a";
      break;
  }
  ?>

This type of question should be referred to a PHP user mailing list
for answering and not to the bug tracking system.  The BTS is for
tracking bugs in packages not.  You are not reporting a bug in php but
are instead just asking a question about php.

Bob

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Message #19 received at 734129-quiet@bugs.debian.org (full text, mbox, reply):

From: jidanni@jidanni.org

To: bob@proulx.com

Cc: 734129-quiet@bugs.debian.org

Subject: Re: Bug#734129: switch($X){case 'Y':trigger_error("can you believe \$X is NOT Y but Z"); }

Date: Sat, 04 Jan 2014 10:25:05 +0800

Yes it is all my fault. Sorry.

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