PHP Fatal error: Cannot redeclare LkWdwrd\MuPluginLoader\Util\rel_path()

[alapiere]

Hi,
I've got an error in logs and in specific custom BO page;

Not sure what caused this.

PHP Fatal error: Cannot redeclare LkWdwrd\MuPluginLoader\Util\rel_path() (previously declared in /www/XX/public/vendor/boxuk/wp-muplugin-loader/src/Util/util.php:23) in /www/XX/public/vendor/boxuk/wp-muplugin-loader/src/Util/util.php on line 23"

  "require": {
     (..)
    "boxuk/wp-muplugin-loader": "*",

 "config": {
  "require-all": true,
    "allow-plugins": {
      (..)
      "boxuk/wp-muplugin-loader": true
    }

if I remove mu-require.php from mu-plugins, it works fine.
Happy to provide any additional troubleshooting instructions if needed

[jdamner]

Hey @alapiere

Do you have any other mu-plugin loader packages in your composer.json file? And would it be possible you're loading the muplugin-loader twice?

[asengerdmk]

@jdamner
Getting the same issue.

error message

PHP Fatal error:  Cannot redeclare LkWdwrd\MuPluginLoader\Util\rel_path() (previously declared in /var/www/html/vendor/boxuk/wp-muplugin-loader/src/Util/util.php:23) in /var/www/html/vendor/boxuk/wp-muplugin-loader/src/Util/util.php on line 23

composer.json

    "require": {
        "composer/installers": "^2.2",
        "johnpbloch/wordpress-core": "6.3.2",
        "wpackagist-plugin/wp-fastest-cache": "^1.2"
    },
    "extra": {
        "force-mu": [
            "wp-fastest-cache"
        ],
     }

Maybe it's because we require the utils here for composer: https://github.com/boxuk/wp-muplugin-loader/blob/master/src/Composer/MuLoaderPlugin.php#L32
And another time when the generated file /wp-content/mu-plugins/mu-require.php calls this file: https://github.com/boxuk/wp-muplugin-loader/blob/master/src/mu-loader.php#L28

After commenting out the latter it worked.

[mikemanger]

For us this seems to be happening when the theme (or plugin) is requiring the vendor/autoload.php file to use other vendored libraries (e.g. tecnickcom/tcpdf). I assume the definitions of this project are getting loaded in then.

I guess a simple, but not very elegant, fix would be to add some class_exists() wrappers.

[zimdin12]

Same problem here.

[alapiere]

I spotted at least 2 cases when this can happen
1/ if some composer subpackage require it
~/public$ composer why boxuk/wp-muplugin-loader
rootpackage/root 1.0.0 requires boxuk/wp-muplugin-loader (*)
subpackage/subpackage dev-master requires boxuk/wp-muplugin-loader (~2)

2/if anywhere in the chain, a class explictely requires , even require_once (?!) , the main autoloader
, like @mikemanger said.
-->
2025/01/03 16:15:52 [error] 55977#55977: *52504 FastCGI sent in stderr: "PHP message: PHP Fatal error: Cannot redeclare LkWdwrd\MuPluginLoader\Util\rel_path() (previously declared in /www/xx/public/vendor/boxuk/wp-muplugin-loader/src/Util/util.php:23) in /www/xx/public/vendor/boxuk/wp-muplugin-loader/src/Util/util.php on line 23" while reading response header from upstream,

yes it "should not" happen , but in real life with multiple dependencies on which you have no control of , it must be handled a bit more carefully, with a non-fatal error and an error_log