ID: 17959
Updated by: [EMAIL PROTECTED]
Reported By: [EMAIL PROTECTED]
-Status: Open
+Status: Analyzed
-Bug Type: Scripting Engine problem
+Bug Type: Documentation problem
Operating System: linux
PHP Version: 4.2.1
-Assigned To:
+Assigned To: hholzgra
New Comment:
think of the "global $p;" construct as a shortcut for
"$p = &$GLOBALS['p'];"
so by assigning a new reference you are breaking the one to the global
variable
so you have to explicitly assign to $GLOBALS["p"] here
(marked as documentation problem)
Previous Comments:
------------------------------------------------------------------------
[2002-07-16 08:40:10] [EMAIL PROTECTED]
<?php
// Here is a slightly modified version of the original
// post (case 3). I hope the lenght of this test-case
// acceptable as i do not know of a shorter example.
//
// Thanks,
// --patrick
// define array we plan to navigate.
$top =
array
(
'name' => 'top',
'A' => array ( 'name' => 'A', ),
'B' => array
(
'name' => 'B',
'B_b' => array ( 'name' => 'B_b', ),
),
);
// setup "parent references" for each of the nodes.
$top['parent'] = null;
$top['A']['parent'] = &$top;
$top['B']['parent'] = &$top;
$top['B']['B_b']['parent'] = &$top['B'];
// setup our reference to $top. $ptr is what should change
// on every call to change_ptr(name).
$ptr = &$top;
// $i and $iref are meant to demonstrate the inconsistency
// of manipulating references w/in functions.
$i = 0;
$iref = &$i;
// change_ptr( name ) does the following w/some verbose
// messages to display the state of variables in question.
//
// if ( ptr[name] )
// ptr = ptr[name];
//
function change_ptr( $name )
{
// This case demonstrates how change_ptr() function fails
// to actually change the value of a global variable $ptr.
//
// Essentially 'global $ptr' seems to only be local to the
// function scope and modifying its value seems to have no
// bearing on the global var $ptr that is of interest.
//
// Please note that the demonstrated behavior is not
// inconsistent with how $iref is treated.
global $ptr;
global $iref;
$iref++;
printf( " change_ptr($name) " );
if ( $ptr[$name] ) {
// Setting up string for later printing.
$before_change =
sprintf( "before: \$ptr['name'] = %s", $ptr['name'] )
. "\n " .
sprintf( " \$GLOBALS['ptr']['name'] = %s",
$GLOBALS['ptr']['name'] );
$ptr = &$ptr[$name];
$after_change =
sprintf( "after: \$ptr['name'] = %s", $ptr['name'] )
. "\n " .
sprintf( " \$GLOBALS['ptr']['name'] = %s",
$GLOBALS['ptr']['name'] );
printf( "<font color=\"green\">CHANGED</font>:\n" );
printf( " %s\n %s", $before_change, $after_change );
}
else
printf( "<font color=\"red\">NO CHANGE!</font>" );
printf( "\n \$iref: $iref" );
printf( "\n \$GLOBALS['iref']: $iref<br>\n" );
}
?>
<pre>
<?
// The first call to change_ptr('B') is expected to change
// globally defined $ptr to become $ptr['B'], hence, the
// 2nd call to the change_ptr('B') should fail since
// $top['B']['B'] does not exist.
change_ptr('B');
change_ptr('B'); // What is going on??
// Why didn't previous call stick?
?>
</pre>
------------------------------------------------------------------------
[2002-07-13 18:29:59] [EMAIL PROTECTED]
Please provide a SHORT reproducing script.
Derick
------------------------------------------------------------------------
[2002-06-25 00:41:53] [EMAIL PROTECTED]
<?php
//
// There seems to be some issues with how array references
// are handled by PHP, unless, my understanding of how
// array()s and references to them are supposed to work is
// seriously flawed.
//
// Unfortunately i don't have enough time on my hands to
// dig through PHP sources.
//
// The source below seems to be a few very simple test-cases
// pointing out the bug that's caused me enough grief.
// Hopefully, someone can use this information in tracking
// down the bug and eventually fixing it.
//
// The following issues can be duplicated on both
// PHP Versions 4.1.2 and 4.2.1
//
// I'm not much concerned about 'Case 1' as I am about
// cases 3 and 4. They seem more serious problems.
//
?>
<? // -- Case 1
// This case demonstrates that $top['B']['B_b']['parent'] loses
// the reference to parent array!
//
$top =
array
(
'name' => 'top',
'parent' => null,
'A' =>
array
(
'name' => 'A',
'parent' => &$top,
),
'B' =>
array
(
'name' => 'B',
'parent' => &$top,
'B_b' =>
array
(
'name' => 'B_b',
'parent' => &$top['B'],
),
),
);
?>
<pre>
case 1:
top:
<?
foreach ( $top as $k => $v ) {
printf( " $k => $v\n" );
}
?>
</pre>
<pre>
top['A']:
<?
foreach ( $top['A'] as $k => $v ) {
printf( " $k => $v\n" );
}
?>
</pre>
<pre>
top['B']:
<?
foreach ( $top['B'] as $k => $v ) {
printf( " $k => $v\n" );
}
?>
</pre>
<pre>
top['B']['B_b']:
<?
foreach ( $top['B']['B_b'] as $k => $v ) {
printf( " $k => $v\n" );
}
//
// What happened to $top['B']['B_b']['parent'] reference?
//
?>
</pre>
<hr align="left" size="5" width="80%">
<? // -- Case 2
// This case shows a work around to above bug.
//
$top =
array
(
'name' => 'top',
//'parent' => null,
'A' =>
array
(
'name' => 'A',
//'parent' => &$top,
),
'B' =>
array
(
'name' => 'B',
//'parent' => &$top,
'B_b' =>
array
(
'name' => 'B_b',
//'parent' => &$top['B'],
),
),
);
$top['parent'] = null;
$top['A']['parent'] = &$top;
$top['B']['parent'] = &$top;
$top['B']['B_b']['parent'] = &$top['B'];
?>
<pre>
case 2:
top:
<?
foreach ( $top as $k => $v ) {
printf( " $k => $v\n" );
}
?>
</pre>
<pre>
top['A']:
<?
foreach ( $top['A'] as $k => $v ) {
printf( " $k => $v\n" );
}
?>
</pre>
<pre>
top['B']:
<?
foreach ( $top['B'] as $k => $v ) {
printf( " $k => $v\n" );
}
?>
</pre>
<pre>
top['B']['B_b']:
<?
foreach ( $top['B']['B_b'] as $k => $v ) {
printf( " $k => $v\n" );
}
?>
</pre>
<hr align="left" size="5" width="80%">
<pre>
case 3:
<? // -- Case 3
// This case demonstrates how change_ptr() function fails to
actually
// change the value of a global variable $ptr.
//
// Essentially 'global $ptr' seems to only be local to the
function
// scope and modifying its value seems to have no bearing on the
// global variable $ptr that we are interested in!!
//
// Please note that the demonstrated behavior is inconsistant with
// how $iref is treated.
//
$ptr = &$top;
$i = 0;
$iref = &$i;
function change_ptr( $name )
{
global $ptr;
global $iref;
$iref++;
printf( " change_ptr($name) " );
if ( $ptr[$name] ) {
$before_change =
sprintf( "before: \$ptr['name'] = %s", $ptr['name'] ) . "\n "
.
sprintf( " \$GLOBALS['ptr']['name'] = %s",
$GLOBALS['ptr']['name'] );
$ptr = &$ptr[$name];
$after_change =
sprintf( "after: \$ptr['name'] = %s", $ptr['name'] ) . "\n "
.
sprintf( " \$GLOBALS['ptr']['name'] = %s",
$GLOBALS['ptr']['name'] );
printf( "<font color=\"green\">CHANGED</font>:\n" );
printf( " %s\n %s", $before_change, $after_change );
}
else
printf( "<font color=\"red\">NO CHANGE!</font>" );
printf( "\n \$iref: $iref<br>\n" );
}
change_ptr('B');
change_ptr('B'); // what is going on?? Why didn't previous call
stick?
?>
</pre>
<hr align="left" size="5" width="80%">
<pre>
case 4:
<? // -- Case 4
// This case shows the expected behavior of 'Case 3'.
//
function change_ptr2( $name )
{
global $iref;
$iref++;
printf( " change_ptr2($name) " );
if ( $GLOBALS['ptr'][$name] ) {
$before_change =
sprintf( "before: \$GLOBALS['ptr']['name'] = %s",
$GLOBALS['ptr']['name'] );
$GLOBALS['ptr'] = &$GLOBALS['ptr'][$name];
$after_change =
sprintf( "after: \$GLOBALS['ptr']['name'] = %s",
$GLOBALS['ptr']['name'] );
printf( "<font color=\"green\">CHANGED</font>:\n" );
printf( " %s\n %s", $before_change, $after_change );
}
else
printf( "<font color=\"red\">NO CHANGE!</font>" );
printf( "\n \$iref: $iref<br>\n" );
}
change_ptr2('B');
change_ptr2('B'); // good! no change
change_ptr2('B_b');
change_ptr2('parent'); // Back to $top['B']
change_ptr2('parent'); // Back to $top
change_ptr2('A'); // This call will cause a problem soon!
change_ptr2('parent');
change_ptr2('B');
change_ptr2('B_b');
// And just as we were doing so well ...
change_ptr2('parent'); // Grrr! What happened!?!?
// apparently the call change_ptr2('A') screws something up.
?>
</pre>
<?
// ex: ai et sw=2 ts=2
?>
------------------------------------------------------------------------
--
Edit this bug report at http://bugs.php.net/?id=17959&edit=1
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