#17309 [Com]: pass by reference in call_user_func

ID: 17309 Comment by: spagmoid at yahoo dot com Reported By: pmoor at netpeople dot ch Status: Bogus Bug Type: Scripting Engine problem Operating System: linux PHP Version: 4.2.1 New Comment: 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) Previous Comments: ------------------------------------------------------------------------ [2002-10-24 16:06:14] 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. ------------------------------------------------------------------------ [2002-07-05 11:34:57] 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 11:34:10] 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 11:32:05] 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 $func_name is an array to call a user method (which is a flaw in PHP :( ) ------------------------------------------------------------------------ [2002-05-20 11:01:03] pmoor at netpeople dot ch i've disabled the "call-time pass-by-reference" option in my configuration file. now, when trying to call_user_func a function with reference-parameters, it won't work, unless i call-time-pass-by-reference my parameters despite the warning. ( this bug might be related to bug #17246 ) here a small example: function pass_by_reference( &$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 ) ------------------------------------------------------------------------ -- Edit this bug report at http://bugs.php.net/?id=17309&edit=1