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Date: Mon, 2 Nov 2015 20:44:11 +0100
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Subject: Re: [PHP-DEV] [Question] Variadic method signature compatibility
 between 5.6 and 7.0
From: dev@mabe.berlin (Marc Bennewitz)

Hi Rowan,

On 11/02/2015 05:41 PM, Rowan Collins wrote:
> Alexander Lisachenko wrote on 02/11/2015 11:12:
>> First definition declares exactly one single parameter, which can be 
>> absent during the method call, so I can even write
>>
>> public static function test() {}
>>
>> Second definition defines zero or more arguments, so it can be also 
>> described by the same signature:
>>
>> public static function test() {}
>
> OK, I got a bit confused with the different optional parameters, and 
> neither your explanation nor Andrea's quite did it for me.
>
> But, I think you're right that this should be compatible, if the rule 
> is "any legal call on the parent should also be legal on the child". 
> Currently, all versions of PHP enforce the following:
>
> - if parent accepts no parameters, child must accept zero, but could 
> accept one or more optional parameters
> - if parent accepts zero or one (an optional parameter), child must 
> accept zero, must accept one, but could accept more (so, two optional 
> parameters is fine; no parameters at all is incompatible)
>
> Thus this is acceptable:
>
> class Foo {
>     public function test() {}
> }
> class Bar extends Foo {
>     public function test($foo = null) {}
> }
>
> But these are all not:
>
> class Foo2 {
>     public function test($foo = null) {}
> }
> class Bar2 extends Foo2 {
>     // Doesn't accept one parameter
>     public function test() {}
> }
> class Baz2 extends Foo2 {
>     // Doesn't accept zero parameters
>     public function test($foo) {}
> }
>
> class Foo3 {
>     public function test() {}
> }
> class Bar3 extends Foo3 {
>     // Doesn't accept zero parameters
>     public function test($foo) {}
> }
>
>
> Variadic signatures count as "zero or more" when the parent accepts 
> only zero:
>
> class Foo4 {
>     public function test() {}
> }
> class Bar4 extends Foo4 {
>     public function test(...$foo) {}
> }
>
> But where the parent accepts "zero or one", the following ought to be 
> compatible because calls with no parameters, and calls with one 
> parameter, would both be valid:
>
> class Foo {
>     public function test($foo = null) {}
> }
> class Bar extends Foo {
>     public function test(...$foo) {}
> }
>
>
> In short, I agree with you that this warning is incorrect, but will 
> leave this here in case anybody else is equally confused (and becomes 
> any less so by reading this...)
>
In my opinion the warning is valid as the one method defines one 
optional argument and the overwritten method would accept no or more 
arguments where the no arguments is wrong:
https://3v4l.org/6eMiu
class Foo {
     public function test($foo = null) {}
}
class Bar extends Foo {
     public function test() {}
}

The first defined argument gets more interesting if it defines a 
type-hint what is not possible to define as variadic:
https://3v4l.org/HQdvI
class Foo {
     public function test(Foo $foo = null) {}
}
class Bar extends Foo {
     public function test(...$bar) {}
}

Additionally this issue can simply be addressed by:
https://3v4l.org/74r3K
class Foo {
     public function test(Foo $foo = null) {}
}
class Bar extends Foo {
     public function test(Foo $foo = null, ...$bar) {}
}

> Regards,

Marc