Migrate Interfaces to use PHP 7.1

[jcchavezs]

Background

Since PHP 5.6 and 7.0 are not supported anylonger, it makes sense to update the library.

Related to https://github.com/opentracing/opentracing-php/issues/74

Ping @cawolf

[piotrooo]

PHP 7.1 is also not supported (https://www.php.net/supported-versions.php), we should start from 7.2.

[cawolf]

I will start migrating to 7.1 level. The only big difference to 7.2 will be the added object type, and the composer dependency, of course.

In the meantime, you can discuss the actual point: whether to migrate to 7.2 directly.

[piotrooo]

Starting with unsupported and legacy version of a PHP is not good in my opinion.

[cawolf]

Besides: I found only 1 file (OpenTracing\Reference), which missed a single return type hint. All interfaces are up-to-date according to both 7.1 and 7.2 specifications.

@jcchavezs , what am I missing?

[jcchavezs]

I think moving to 7.1 is good enough for now as it does not drag us to do retrocompatibility stuff like we did for PHP 5.6. Let's keep in mind that we should ease the migration for the implementations.

[cawolf]

Besides: I found only 1 file (OpenTracing\Reference), which missed a single return type hint. All interfaces are up-to-date according to both 7.1 and 7.2 specifications.

@jcchavezs , what am I missing?

ping @jcchavezs :)

[jcchavezs]

@cawolf I would say the best way to make sure we are not missing types is including phpstan checks. Are you up to that? For a reference you can see https://github.com/openzipkin/zipkin-php/blob/master/composer.json#L55

[cawolf]

Roger that :)

[cawolf]

related to #93