Req #53648 [NEW]: Allow __toString() to throw exceptions

From: Date: Tue, 04 Jan 2011 13:45:30 +0000
Subject: Req #53648 [NEW]: Allow __toString() to throw exceptions
Groups: php.bugs 
Request: Send a blank email to php-bugs+get-157557@lists.php.net to get a copy of this message 
From:             
Operating system: 
PHP version:      5.3.4
Package:          Class/Object related
Bug Type:         Feature/Change Request
Bug description:Allow __toString() to throw exceptions

Description:
------------
Currently, when casting an object with __toString() to a string,
__toString() is not allowed to throw an exception.
Trying to do so triggers an E_ERROR "Method %s::__toString() must not throw
an exception".
IMHO, this is counter-intuitive, especially since calling that object's
__toString() method directly would correctly throw the exception.

I propose to allow __toString() to throw exceptions.

Note: this was already reported in http://bugs.php.net/bug.php?id=50699 but
marked as bogus with the only explanation being "__toString must not
throw".
So, I'm marking this as a feature request rather than a bug, since the
current behaviour seems to be expected (though it is not documented in
http://php.net/manual/en/language.oop5.magic.php#language.oop5.magic.tostring).

I also found this entry
http://stackoverflow.com/questions/2429642/why-its-impossible-to-throw-exception-from-tostring
which cites Johannes saying this requires major changes in the code.
However, the article mentioned is from 2007 and I think the limitations in
ZE that prevented this to be implemented were lifted since then.

I'm not very versed in PHP's inner workings, but attached is a tentative
patch which seems to fix this issue.

Test script:
---------------
<?php

class CustomException
extends Exception
{
}

class Foo
{
    public function __toString()
    {
        throw new CustomException('oops!');
    }
}


$foo = new Foo();
try {
    var_dump((string) $foo);
}
catch (CustomException $e) {
    var_dump($e);
}

?>

Expected result:
----------------
object(CustomException)#2 (7) {
  ["message":protected]=>
  string(5) "oops!"
  ["string":"Exception":private]=>
  string(0) ""
  ["code":protected]=>
  int(0)
  ["file":protected]=>
  string(17) "/tmp/toString.php"
  ["line":protected]=>
  int(65)
  ["trace":"Exception":private]=>
  array(1) {
    [0]=>
    array(6) {
      ["file"]=>
      string(17) "/tmp/toString.php"
      ["line"]=>
      int(71)
      ["function"]=>
      string(10) "__toString"
      ["class"]=>
      string(3) "Foo"
      ["type"]=>
      string(2) "->"
      ["args"]=>
      array(0) {
      }
    }
  }
  ["previous":"Exception":private]=>
  NULL
}


Actual result:
--------------
PHP Fatal error:  Method Foo::__toString() must not throw an exception in
/tmp/toString.php on line 0
PHP Stack trace:
PHP   1. {main}() /tmp/toString.php:0

-- 
Edit bug report at http://bugs.php.net/bug.php?id=53648&edit=1
-- 
Try a snapshot (PHP 5.2):            http://bugs.php.net/fix.php?id=53648&r=trysnapshot52
Try a snapshot (PHP 5.3):            http://bugs.php.net/fix.php?id=53648&r=trysnapshot53
Try a snapshot (trunk):              http://bugs.php.net/fix.php?id=53648&r=trysnapshottrunk
Fixed in SVN:                        http://bugs.php.net/fix.php?id=53648&r=fixed
Fixed in SVN and need be documented: http://bugs.php.net/fix.php?id=53648&r=needdocs
Fixed in release:                    http://bugs.php.net/fix.php?id=53648&r=alreadyfixed
Need backtrace:                      http://bugs.php.net/fix.php?id=53648&r=needtrace
Need Reproduce Script:               http://bugs.php.net/fix.php?id=53648&r=needscript
Try newer version:                   http://bugs.php.net/fix.php?id=53648&r=oldversion
Not developer issue:                 http://bugs.php.net/fix.php?id=53648&r=support
Expected behavior:                   http://bugs.php.net/fix.php?id=53648&r=notwrong
Not enough info:                     http://bugs.php.net/fix.php?id=53648&r=notenoughinfo
Submitted twice:                     http://bugs.php.net/fix.php?id=53648&r=submittedtwice
register_globals:                    http://bugs.php.net/fix.php?id=53648&r=globals
PHP 4 support discontinued:          http://bugs.php.net/fix.php?id=53648&r=php4
Daylight Savings:                    http://bugs.php.net/fix.php?id=53648&r=dst
IIS Stability:                       http://bugs.php.net/fix.php?id=53648&r=isapi
Install GNU Sed:                     http://bugs.php.net/fix.php?id=53648&r=gnused
Floating point limitations:          http://bugs.php.net/fix.php?id=53648&r=float
No Zend Extensions:                  http://bugs.php.net/fix.php?id=53648&r=nozend
MySQL Configuration Error:           http://bugs.php.net/fix.php?id=53648&r=mysqlcfg

Thread (14 messages)

« previous php.bugs (#157557) next »