3.0 | Drop support for PHP < 7.0

Drop support for PHP < 7.0 [1]

Update Composer version requirements.
Remove PHP 5.x specific Composer script.
Stop running tests/linting in CI against PHP 5.6.
Update documentation.
Update some tests.

Drop support for PHP < 7.0 [2]

Remove two polyfilled PHP native classes, which are no longer needed.

Drop support for PHP < 7.0 [3]

Simplify the tests for the AssertObjectEquals trait.

These tests had two flavours:

The base test class which is compatible with PHP 7.0 and higher. This test class uses fixtures with return type declarations.
A mirror test class which is compatible with PHP 5.6+ with PHPUnit < 9.4.0. This test class uses fixtures without return type declarations to make the tests runnable on PHP < 7.0.

This mirror test class, and its associated test fixtures, are no longer needed now support for PHP < 7.0 is being dropped.

Drop support for PHP < 7.0 [4]

In the original implementation of the assertObjectEquals() polyfill, the polyfill could not mirror the PHPUnit native implementation completely as that required support for return types, which was only added in PHP 7.0, while the polyfill was introduced in PHPUnit Polyfills 1.0, which still supported PHP 5.5.

So instead of checking whether the "comparator" method had a return type declared and verifying that this return type complied with the requirements set by PHPUnit, the polyfill originally checked whether the returned value complied with the required type.

Now support for PHP < 7.0 is being dropped, the assertObjectEquals() polyfill can be updated to fix this implementation difference.

Includes unit tests for the changed functionality/new logic paths throwing exceptions. Includes updated documentation in the README.

Refs:

38
sebastianbergmann/phpunit#4707
sebastianbergmann/phpunit#4467
sebastianbergmann/phpunit#4707
sebastianbergmann/phpunit@1dba8c3
sebastianbergmann/phpunit@6099c5e

Yoast / PHPUnit-Polyfills