Deprecate required param after optional

[nikic]

This addresses https://bugs.php.net/bug.php?id=53399.

Historically, having an "optional" parameter before a required one was useful for poor man's nullable types. That is, one could write function test(FooBar $param = null, $param2) to get an effective ?FooBar typehint on PHP versions that did not natively support it.

Since we've had nullable types since PHP 7.1 now, having a required parameter after an optional one is increasingly likely a bug rather than an intentional workaround, so we should throw a warning for this case.

[carusogabriel]

👍 For this one

[BackEndTea]

Maybe the message should also say this will become an error in a later PHP version. (If that is the plan)

[nikic]

Per the ML discussion, I've changed this to throw a deprecation warning instead.

[ostrolucky]

This looks controversial to me, there should be an RFC. string foo = null is common in other languages.

[Girgias]

This looks controversial to me, there should be an RFC. string foo = null is common in other languages.

This is not to remove this altogether, it's to deprecate the fact that you have a default value on some parameters before some which don't, meaning that you have an optional param before mandatory ones.

[ostrolucky]

I stand corrected, that shouldn't be controversial 👍

[vvval]

And what if an optional param doesn't have a type?

/**
 * @param mixed|null $param
 * @param            $param2
 */
function test($param = null, $param2)

[Girgias]

And what if an optional param doesn't have a type?

/**
 * @param mixed|null $param
 * @param            $param2
 */
function test($param = null, $param2)

This case is also covered and would be deprecated.

[ostrolucky]

And what if an optional param doesn't have a type?

/**
 * @param mixed|null $param
 * @param            $param2
 */
function test($param = null, $param2)

This case is also covered and would be deprecated.

What's the alternative for that though? There is no mixed type so you can't replace it with function test(?mixed $param, $param)

edit: we can do function test($param, $param2) of course 🤦‍♂

[Girgias]

And what if an optional param doesn't have a type?

/**
 * @param mixed|null $param
 * @param            $param2
 */
function test($param = null, $param2)

This case is also covered and would be deprecated.

What's the alternative for that though? There is no mixed type so you can't replace it with function test(?mixed $param, $param)

The alternative is to have your optional parameter in second place instead of first.

[ostrolucky]

You can't swap arguments willy nilly, that would cause BC breaks.

[Girgias]

You can't swap arguments willy nilly, that would cause BC breaks.

There will be a full PHP major cycle for libraries to fix this.
And BC should not be kept for clearly nonsensical code IMHO.

[nikic]

function test($param = null, $param2) is strictly equivalent to function test($param, $param2). You can just drop the useless and confusing = null, there are no BC implications whatsoever for that case.