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Bug #18437 Return value from custom error handler passed back to calling script
Submitted: 2002-07-19 11:50 UTC Modified: 2002-07-26 08:51 UTC
From: duncan at emarketeers dot com Assigned:
Status: Not a bug Package: Scripting Engine problem
PHP Version: 4.2.1 OS: Linux
Private report: No CVE-ID: None
View Developer Edit
 [2002-07-19 11:50 UTC] duncan at emarketeers dot com 
If you set an error handler which returns rather than dying, then the return value of the handler is passed back to the script in place of the expected value iff the statement which raised the error is followed by a function call. Additionally, execution of the remainder of the statement is aborted.

This means that e.g. if you reference an unset variable as part of an expression which contains function calls, the expression will evaluate to the return value of the error handler, which is NOT the behaviour if you have not got an error handler installed.

i.e. the following will print

This fails: --ERROR-- <br>
But this works: some text <br>



<?
function myErrorHandler ($errno, $errstr, $errfile, $errline) {
        switch ($errno) {
                case E_USER_ERROR: {
                        echo "A fatal error occurred";
                        exit;
                }
                default : {
                }
        }
        return "--ERROR--";
}
define (FATAL,E_USER_ERROR);
define (ERROR,E_USER_WARNING);
define (WARNING,E_USER_NOTICE);

// set the error reporting level for this script
error_reporting (FATAL | ERROR | WARNING);

set_error_handler("myErrorHandler");
$c = "some text";
$a = $b . trim($c);
echo "This fails: $a <br>";

$a = $b . $c;

echo "But this works: $a <br>\n";

?>

My config line was:

./configure  --with-xslt-sablot --enable-xslt --with-mysql --enable-mailparse --enable-mbstring

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 [2002-07-19 12:33 UTC] sniper@php.net 
This is the output with PHP 4.3.0-dev:

"This fails: some text <br>But this works: some text <br>"

(I don't understand your example..you never trigger those error levels..)
 [2002-07-24 08:42 UTC] duncan at emarketeers dot com 
Glad to see it works in an unstable alpha. But on a  
production release it is broken.  
  
You do trigger those error levels. You get E_NOTICE passed 
through to the error handler when e.g. you try to 
reference an undefined variable, as in the example. Even 
though you didn't ask for it. 
 
While we're on the subject, why can't user error-handlers 
catch E_ERROR? If I'm in the middle of a complicated 
database transaction I'd at least like the chance to be 
able to tidy up.
 [2002-07-24 19:48 UTC] sniper@php.net 
Sorry, but the bug system is not the appropriate forum for asking
support questions. Your problem does not imply a bug in PHP itself.
For a list of more appropriate places to ask for help using PHP,
please visit http://www.php.net/support.php

Thank you for your interest in PHP.
 [2002-07-26 08:51 UTC] duncan at emarketeers dot com 
I would have thought that an error handler which doesn't 
catch errors has a bug in it.
 [2004-02-06 14:10 UTC] joop dot vriend at ddnh dot nl 
This WAS really NOT a bogus bug! It is solved though in PHP 4.3.4 (or earlier in 4.3.x?).

We have exactly the same - incorrect - behaviour when setting our own error handler in PHP 4.2.3. The following test case shows this clearly.

1) NO user defined error handler:

<?php
    $c = "some text";
    $a = $b . trim($c);

    echo "a=";
    echo $a;
?>

This code produces the output

a=some text

2) WITH user defined error handler:

<?php
    function ourOwnErrorHandler() {
    }

    $old_error_handler = set_error_handler("ourOwnErrorHandler");

    $c = "some text";
    $a = $b . trim($c);

    echo "a=";
    echo $a;
?>

This code produces the output

a=


This was tested on:

PHP Version 4.2.3

System	Linux 2.4.1 #1 SMP Thu Oct 25 16:10:32 CEST 2001 i686 unknown
Build Date	Sep 20 2002 12:00:27
Configure Command	'./configure' '--with-config-file-path=/usr/local/apache/conf' '--with-apache=/usr/local/src/apache' '--with-jpeg-dir=/usr/local/src/jpeg-6b' '--with-png-dir=/usr/local/lib' '--with-zlib-dir=/usr/local/lib' '--with-zlib' '--with-gd=/usr/local/src/gd' '--with-oci8=/u01/app/oracle/product/8.1.7' '--with-oracle=/u01/app/oracle/product/8.1.7' '--enable-dbase' '--with-mcrypt' '--with-mhash' '--with-imap'

Joop Vriend.
 
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