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Request #70296 pass by reference: switch back to call time
Submitted: 2015-08-18 23:41 UTC Modified: 2015-08-19 00:40 UTC
From: o dot rijkers at gmail dot com Assigned:
Status: Wont fix Package: Unknown/Other Function
PHP Version: Irrelevant OS:
Private report: No CVE-ID: None
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 [2015-08-18 23:41 UTC] o dot rijkers at gmail dot com 
Description:
------------
In the latest version the pass by reference is moved to the function declaration:

function myFunct(&$arg) {...}

This results in several limitations:
1. the $arg argument can only be a call by reference.
   The pass by reference requirement may be dependent of the location where
   the function is called (I just run into this, hence this request), i.e.
   sometimes I just want to call myFunc($a); and I don't want $a to be changed.
2. it is not possible to pass an expression or literal as the first argument.
3. it is not possible to define a default value (other than null) and omit the
   argument when calling the function, e.g. myFunc();

It should never be the responsibility of a function to enforce a pass by reference. At best it could provide the option of a pass by reference argument. This greatly improves the flexibility, especially for library developers.


Test script:
---------------
function myFunc(&$arg = 1) {}
function yourFunc($arg) {}

myFunc($a);    // no pass by reference as it is not desired
myFunc(3);     // no pass by reference as it is not desired
myFunc();      // no pass by reference as it is not desired
myfunc(&$a);   // pass by reference as it is required by the caller and
               // the option of pass by reference is provided by the function

yourFunc(&$a); // no pass by reference as this option is not provided by the
               // function declaration

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 [2015-08-19 00:32 UTC] rasmus@php.net
-Status: Open +Status: Wont fix
 [2015-08-19 00:32 UTC] rasmus@php.net 
Latest version? This was changed in PHP 5.3.0 in 2009. There are a number of reasons why it needs to be this way, sorry.
 [2015-08-19 00:40 UTC] requinix@php.net 
Rasmus beat me to it.

When a function defines a certain signature, being a combination of the parameters, their types, whether they are by-reference or not, and their default values, you need to obey the signature when you call it. That signature forms a contract that you, the developer, need to obey. If a function says a parameter needs to be passed by reference then there is a reason for it and you need to pass your argument by reference. You may not decide that you want to call the function in a different way than it was intended.

Meanwhile if the developer who created the function is abusing the concept of references, that's a different problem.

> 1. the $arg argument can only be a call by reference.
Right. Because the function says that argument has to be by reference.

> The pass by reference requirement may be dependent of the location where
> the function is called (I just run into this, hence this request), i.e.
> sometimes I just want to call myFunc($a); and I don't want $a to be changed
The function clearly intends to modify the variable - or at least have the capability to do so. If you don't want your $a to be modified then make a copy and pass that to the function instead.

> 2. it is not possible to pass an expression or literal as the first argument.
Correct. If the function wants a variable by reference then it means to modify the variable and so passing a non-variable does not make sense.

> 3. it is not possible to define a default value (other than null) and omit the
> argument when calling the function, e.g. myFunc();
Sure it is. https://3v4l.org/eQ6e4


See also bug #70278 which someone made just a couple days ago.
 
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