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Date: Mon, 23 Feb 2015 20:32:19 +0100
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Subject: Proposal: deprecate undefined passed arguments
From: dev@mabe.berlin (Marc Bennewitz)

Hi all,

Because the feature freeze for PHP 7 is near I like to know your 
thoughts about one more change in passing arguments. Sure this one would 
introduce one more deprecated message / BC break but this one s for 
reducing BC break in the future!

Currently a caller can pass undefined arguments as much he like. Such 
passed arguments are only visible by the callee using 
func_get_args/func_num_args but the need for such function definitions 
has been gone with argument unpacking feature. The other rare 
possibility for ignoring passed arguments by callables from functions 
like array_walk has been gone, too, with the introduction of clusures.

By the way we already have internal functions triggering warnings on 
unknown arguments. This is also an unneeded inconsistency and more it's 
invisible by the user without testing each function for it.

At least simply ignoring passed arguments is a violation as described in 
the following examples (http://3v4l.org/U2lnf):

class Calculator {
     public function calc($v) {
         return $v + 1;
     }
}

class MyCalculator extends Calculator {
     public function calc($v1, $v2 = 0) {
         return parent::calc($v1) + $v2;
     }
}

function calcArray(array $values, Calculator $calculator) {
     foreach ($values as &$v) {
         $v = $calculator->calc($v, $v); // Second argument is wrong !!
     }
     return $values;
}

$ar = [1,2,3];
var_dump(calcArray($ar, new Calculator));   // ignores the second argument
var_dump(calcArray($ar, new MyCalculator)); // UNEXPECTED:  the second 
argument will be used


Both calculators should be 100% compatible but they aren't as the 
function "calcArray" shows.


So because of the described issues with the existing code base I like to 
propose the change to no longer ignore undefined arguments and introduce 
E_DEPRECATED messages if a function get's an undefined argument. So the 
user get enough time to fix their code before throwing errors in this 
case in PHP 8.

As this should be consistent over the engine I would propose this change 
for user defined functions and for internal functions as well.

Again, yes this one would introduces one more BC break but first this 
would be deprecated before disabled and next it's for reducing BC in the 
future.

Marc