Change only the basic in the PHP migration from 7.4 to 8.1

[amendiola]

Hi,

I am trying to migrate some PHP projects from 7.4 to 8.1 version with Rector and it is a fantastic tool, but I have a little problem.
When I execute rector it modifies a lot of files by different rules, but I don't want apply the most of these changes.
¿Are any way to only apply the necessary changes (the deprecations) in a migration from PHP 7.4 to PHP 8.1 ?

Thank you very much.

[mspirkov]

It seems that there is no separate set that includes only rules for fixing deprecation errors.
I would recommend that you select the necessary rules from this list: https://getrector.com/find-rule?activeRectorSetGroup=php

[Kenneth-Sills]

I've found myself wanting this in the past as well, since I maintain some very large legacy projects.

If someone wants, they can see if @TomasVotruba would bless a separate set or flag for this and then open an issue / PR.

My changes here located most of the rules for deprecations (though not strictly all of the rules for required changes). Unfortunately, the only indication for these right now are providedMinPhpVersion() returning a PhpVersionFeature::DEPRECATE_* constant; otherwise, you need to review the whole rule list.

[signor-pedro]

This is especially needed in larger companies/corporations, where deploys are frequently 2-phase workflows:

• allow to deploy on higher version, e.g. "php": ">=8.4 <=8.5"
• deploy on 8.5
• observe for some time and when OK, tighten constraint to php": "8.5.*"

Only the last step lets you use the new language features.

The ideal solution: run rector with a --bc-only flag / dedicated BC-only sets.

Workaround: I currently pass the --dry-run output to Claude and let Claude decide whether the proposed change fixes BC/deprecations. This is costly and ugly 😰

[Kenneth-Sills]

You can kind-of do this now, order is important:

return RectorConfig::configure()
    // ...
    ->withSets([
        LevelSetList::UP_TO_PHP_85,
    ])
    ->withPhpVersion(PhpVersion::PHP_74);

Rector will run all the rules in the upgrade set while skipping any whose resolution is not compatible with that explicitly specified PHP version. So push this, do the cutover and monitor, then remove that last line.

However, as noted in #9646, Rector will not run any deprecation rules for your upgrade targets, so you'll have to tank the deprecation notices in your logs during the cutover phase.

To be totally clear, it should still run rules for actual breaking changes.

Also, if you're not aware, PhpStan also supports explicit version ranges for feature detection. I'd recommend using Symfony's PHP polyfills at runtime when using it, too. They can get sneakily included by a dev dependency and trick PhpStan into thinking you have those functions available.

[signor-pedro]

Thanks for the wonderful write-up, especially the dev-dependency warning.