Class not found error with events

It is PHP's specification.

When you use namespacing, the classname is  \App\Events\Load_config.
When you specify the classname in a string, you can also write App\Events\Load_config.
If you write Load_config in a string, it means \Load_config and it is the different namespace.

If you use an IDE like PhpStorm and ::class constant, you can write it as \App\Events\Load_config::class,
and IDE can auto complete the classname.

Code:

Events::on('post_controller_constructor', [\App\Events\Load_config::class, 'load_config']); 

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