I'm ok with this.

I am also ok with this when speaking about my own installations.

But keep in mind that I introduced a hard check for minimum PHP version in version 2.13.0 to fix 0024128.
So upgrading from 2.x 2.20.0 would stop some (maybe even quite a lot) of installations.

The general problem is, that we don't offer some kind of LTS version.

keep in mind that I introduced a hard check for minimum PHP version

Well if we require a minimum version, then I think it's normal that the software should fail with a message when the requirement is not met.

Even if technically, MantisBT would still work with older PHP versions, we can always instruct users who get stuck because they can't upgrade PHP on their server for whatever reason, to try - at their own risk of course - to change value of PHP_MIN_VERSION in their config.

to change value of PHP_MIN_VERSION in their config

Not possible at the moment. The check is done before config_inc.php is included. There was a good reason to check it in a very early state.
See also discussion on the PR https://github.com/mantisbt/mantisbt/pull/1318

I always assumed that 2.0.0 we had PHP 7 as the target version, and support for PHP 5.x was best effort. Given that all 5.x are out of support, I think we should make PHP 7 a hard requirement and move on.

Please do not underestimate the impact on users... and make this change very explicit.
I've found this ticket "by chance"... and i'm currently preparing my whole site to be PHP7 capable in order to upgrade to PHP7 before it gets released.... which takes me a lot of code rewritting, in particular to move from mysql to mysqli extension...

https://www.mantisbt.org/docs/master/en-US/Admin_Guide/html-desktop/#admin.install.requirements

to be updated

@Kyle_Katarn what has to be updated?

The above mentionned web page, once PHP 7 becomes required.

Based on the general consensus, I'm planning to implement this in the next release (2.25.0).

Note: Xenial will enter extended support maintenance mode in April 2021, at which point the oldest LTS release with standard support will be 18.04 "Bionic Beaver" which is on PHP 7.2 [1] so we might go through this again in a few months.

And now PHP 8 is out. Does Mantis support PHP 8? If not, such support would probably be easier dropping 5.x support.

Does Mantis support PHP 8?

I've been running Mantis on PHP 8 for a few weeks now, so I would say yes.

So far I've mainly encountered a few fairly minor issues (e.g. depreprecation, system notices, etc), with the exception of 0027806 (which has been fixed in 2.24.4, along with most of the aforementioned issues).

Check issues tagged with PHP 8 for details.

@dregad to give users a chance to prepare the upgrade of their ennvironment, I would prefer if we

• cut 2.25.0 ASAP
• announce that 2.25.x will be the last version that supports PHP < 7

announce that 2.25.x will be the last version that supports PHP < 7

The announcement is out

• Blog https://mantisbt.org/blog/archives/mantisbt/678
• Gitter https://gitter.im/mantisbt/mantisbt?at=5ff4e9cac746c6431cf988f2

PR https://github.com/mantisbt/mantisbt/pull/1742

2 years have passed and 2.26.0 could not be released as planned.

Targeting PHP 7.0 as minimum supported version does not make much sense in 2023, so as discussed with the team, we'll set PHP 7.2 as minimum supported version for MantisBT 2.26.0; 0032797 was opened to track this.

This issue's summary was changed to Drop support for PHP 5.x, so both issues can coexist on the Changelog without bringing confusion.