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Bug #17309 pass by reference in call_user_func
Submitted: 2002-05-20 11:01 UTC Modified: 2002-10-24 16:06 UTC
Votes:3
Avg. Score:4.3 ± 0.5
Reproduced:3 of 3 (100.0%)
Same Version:1 (33.3%)
Same OS:1 (33.3%)
From: pmoor at netpeople dot ch Assigned:
Status: Not a bug Package: Scripting Engine problem
PHP Version: 4.2.1 OS: linux
Private report: No CVE-ID: None
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 [2002-05-20 11:01 UTC] pmoor at netpeople dot ch 
i've disabled the "call-time pass-by-reference" option in my configuration file.
now, when trying to call_user_func a function with reference-parameters, it won't work, unless i call-time-pass-by-reference my parameters despite the warning.

( this bug might be related to bug #17246 )

here a small example:

function pass_by_reference( &$param ) {
	$param[] = "another entry";
}

$data = array( "a first entry" );
call_user_func( "pass_by_reference", $data );
var_dump($data);	// $data contains only one element ( "a first entry" ) ( == unexpected behaviour )

$data = array( "a first entry" );
call_user_func( "pass_by_reference", &$data ); // Warning: Call-time pass-by-reference has been deprecated - argument passed by value; ...
var_dump($data);	// $data contains both elements ( "a first entry", "another entry" ) ( == expected behaviour )

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 [2002-07-05 11:32 UTC] bram at totalgsm dot net 
A workaround might be using variable function name like

$func_name = 'pass_by_reference';
$funcname($data);

However this doesn't work if the $func_name is an array to call a user method (which is a flaw in PHP :( )
 [2002-07-05 11:34 UTC] bram at totalgsm dot net 
This might be a duplicate of: 
http://bugs.php.net/bug.php?id=17246

However, this test case is clearer.
 [2002-07-05 11:34 UTC] bram at totalgsm dot net 
This might be a duplicate of: 
http://bugs.php.net/bug.php?id=17246

However, this test case is clearer.
 [2002-10-24 16:06 UTC] iliaa@php.net 
Thank you for taking the time to write to us, but this is not
a bug. Please double-check the documentation available at
http://www.php.net/manual/ and the instructions on how to report
a bug at http://bugs.php.net/how-to-report.php

When you do ' call_user_func("pass_by_reference", $data ); ' you actually pass the $data variable to the call_user_func first and that function will internally pass $data to the function specified in the first argument. Unless $data is passed to call_user_func by reference, the call_user_func simply makes a copy of the $data variable and passes that copy to the pass_by_reference function. Hence the 'invalid' output, which you see.
If you do ' pass_by_reference( $data ); ' it works, because the function has been defined to accept the parameter by reference.
 [2003-08-30 16:28 UTC] spagmoid at yahoo dot com 
This is a good example of why the warning against call-time pass by reference is a bad idea.  Any function that accepts a reference should be required to also have the parms use & at call time.  And references should be allowed as optional parameters ie:

function Blah(&$MayBeBlank=0)
 
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