Introduce PHP 7 strict typing

[szepeviktor]

It raises overall code quality.
https://www.php.net/manual/en/control-structures.declare.php

Please consider adding declare(strict_types=1); to every PHP file.

[robbieaverill]

We've agreed to introduce PHP 7.1 as the minimum requirement for SilverStripe 4.5 onwards (from the 4 branch at time of writing) and PHP 7.2 (at time of writing) in SilverStripe 5.x in the master branch.

With SilverStripe 5.x changes we can break APIs, but in the meantime we'll need to keep APIs semver compliant in 4.x releases. For this reason, yes we can add strict typing for new APIs we write, but I don't think we can add it to existing code in the 4.x line. In 5.x we can probably start doing it in bulk.

Is this something you'd like to contribute to? If not, we could chalk it up to a development practice and close the issue for now.

[szepeviktor]

It is very easy:

composer require slevomat/coding-standard
vendor/bin/phpcbf --standard=vendor/slevomat/coding-standard/SlevomatCodingStandard --sniffs=SlevomatCodingStandard.TypeHints.DeclareStrictTypes src/ tests/

May I send a PR?

[robbieaverill]

Yes please, into the master branch :-)

[szepeviktor]

Done.

You could add the above phpcs sniff to sustain strict typing.

[sminnee]

Hang on. I would note that declare(strict_types) isn't an API breakage. Making our APIs return consistent types would be, and it might simplify the creation of code to comply with strict_typing, but in some ways I'd prefer a partial application of strict_types in 4 that we polish in 5, rather than a massive divergence between 4 and 5 on this point.

[robbieaverill]

We can already add it to new APIs in SS4

[sminnee]

Note that declare(strict_types) applies to methods being called, not methods being defined.

The latter is the domain of type definitions on method signatures.