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Date: Sat, 28 Mar 2020 08:44:51 +0100
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Subject: Interfaces and ReflectionMethod::isConstructor()
From: sebastian@php.net (Sebastian Bergmann)

I recently received a bug report for PHPUnit [1] that with PHP 8 test
doubles (test stubs or mock objects) can no longer be created for
interfaces that declare a constructor.

I was able to reproduce this [2] and learned that PHPUnit's
canMockMethod() [3] returns a different result on PHP 8 compared to PHP
7. This is due to the return value of ReflectionMethod::isConstructor()
when the ReflectionMethod object was created for an interface.

Here is a minimal, self-contained, reproducing test case:

<?php
interface I
{
    public function __construct();
}

var_dump((new ReflectionMethod(I::class, '__construct'))->isConstructor());

The code shown above yields the following result:

* bool(true) for PHP 5.0.0 and PHP 5.0.1
* bool(false) for PHP 5.0.2 through PHP 7.4.4
* bool(true) for PHP 8.0-dev

I think that the behaviour in PHP 8 (and PHP 5.0.0 and PHP 5.0.1) is
correct. But I also think that constructor declarations have no place in
interfaces ... so I am confused. Which is why I did not open a ticket on
bugs.php.net and bring this topic to this list instead.

To the best of my knowledge, this change in behaviour of isConstructor()
between PHP 7 and PHP 8 is not yet documented. If it is intentional and
here to stay then it should be documented.

I can deal with this in PHPUnit's code either way, but need to know what
the plan here is.

Thanks!
Sebastian

-- 
[1] https://github.com/sebastianbergmann/phpunit/issues/4139
[2]
https://github.com/sebastianbergmann/phpunit/issues/4139#issuecomment-605407253
[3]
https://github.com/sebastianbergmann/phpunit/blob/9.0.1/src/Framework/MockObject/Generator.php#L861