Drop support for PHP 7.3

[oliverklee]

PHP 7.3 has reached its end of life:
https://www.php.net/supported-versions.php

[ADDISON74]

... but is still maintained in Debian 10 till 2024.

[JakeQZ]

Is there any reason to drop support for an EOL PHP version if it has no issues or lack of language features we want to make use of moving forwards?

If there is nothing in our immediate dev pipeline that would be blocked by maintaining PHP 7.3 support, and there are compatible versions of all dependencies, why drop PHP 7.3 support?

We can always make an additional major version release to deprecate a PHP version as and when needed. We don't have to stick to PHP's release cycle.

[JakeQZ]

We don't have to stick to PHP's release cycle.

Also, if we make a realease which only adds support for a new PHP version, and doesn't drop support for anything, it should be a minor release according to SemVer.

However, we have already removed support for PHP 7.2 from the trunk, and it's a slight PITA creating a branch for a release, so I suggest that the next release supporting PHP 8.2 will be 7.0.

But next year when we make a release to support PHP 8.3 (or 9.0), it can be version 7.1, if we have no reason to drop PHP 7.3 support.

Many website owners would prefer to keep an EOL PHP version they know works. If it ain't broke, don't fix it. There will still be security patches.

IMO we should support obsolete PHP versions as much as possible, as long as it does not impinge on us.

[JakeQZ]

Added blocked label. Rationale for the need to do this is required to unblock :)

[oliverklee]

Is there any reason to drop support for an EOL PHP version if it has no issues or lack of language features we want to make use of moving forwards?

Mostly for two reasons:

1. problems with PHPUnit (or any other of our dev or non-dev dependencies) not running on our lowest supported PHP version anymore (which currently is not the case - PHPUnit 9.x runs on PHP 7.3)
2. me itching to use more expressive, more strict PHP features of newer versions (which is a personal thing for me, and I'm trying to hold back with this)

IMO we should support obsolete PHP versions as much as possible, as long as it does not impinge on us.

Agreed.

[JakeQZ]

The main issue here is to be able to use PHPUnit 10.x. We can't do that without ditching PHP 7.3.

It is a shame that PHPUnit does not support a wider range of PHP versions, but it is what it is and we are where we are.

We would like to use PHPUnit 10.x. I think we need to make this change.

[oliverklee]

As long as we don't need any particular feature that has been introduced with PHPUnit 10, I'd also be fine with staying on PHPUnit 9 for quite some time (now that Sebastian Bergmann has introduced the "life support" approach to PHPUnit 8 and 9, i.e., those versions will continue to work with newer PHP versions if at all possible, even if they do not support some language features introduced in newer PHP versions).

[JakeQZ]

See also #1206 and #1207.

[JakeQZ]

Changing milestone to 'backlog' on basis of comments here and in #1242. We will drop support for older versions as and when we need to, but won't plan to do so without good reason.