I just took a project from a couple of months ago which was made in Laravel. This project also utilizes Laravel Voyager - the admin panel package.
After browsing to http://example.com/admin, I got this weird error which came out of nowhere and I'm also unsure how to debug it. It looks like this:
Fatal error: Cannot declare class Symfony\Component\HttpFoundation\AcceptHeader, because the name is already in use in /c/Users/User/Code/example-website/vendor/symfony/http-foundation/AcceptHeader.php on line 22
Fatal error: Uncaught Error: Class 'Symfony\Component\HttpFoundation\AcceptHeaderItem' not found in /c/Users/User/Code/example-website/vendor/symfony/http-foundation/AcceptHeader.php:61 Stack trace: #0 [internal function]: Symfony\Component\HttpFoundation\AcceptHeader::Symfony\Component\HttpFoundation\{closure}(Array) #1 /c/Users/User/Code/example-website/vendor/symfony/http-foundation/AcceptHeader.php(57): array_map(Object(Closure), Array) #2 /c/Users/User/Code/example-website/vendor/symfony/http-foundation/Request.php(1664): Symfony\Component\HttpFoundation\AcceptHeader::fromString('text/html,appli...') #3 /c/Users/User/Code/example-website/vendor/laravel/framework/src/Illuminate/Http/Concerns/InteractsWithContentTypes.php(54): Symfony\Component\HttpFoundation\Request->getAcceptableContentTypes() #4 /c/Users/User/Code/example-website/vendor/laravel/framework/src/Illuminate/Http/Concerns/InteractsWithContentTypes.php(44): Illuminate\Http\Request->wantsJson() #5 /c/Users/User/Code/example-website/vendor/laravel/framework/src/Illumina in /c/Users/User/Code/example-website/vendor/symfony/http-foundation/AcceptHeader.php on line 61
This error is very expected and I've never seen it before in my project (or anywhere else for that matter).
How can I debug this issue?
As a sanity check, delete the vendor directory and then run composer install to re-fetch your dependencies and see if the error is resolved. If not, then attempt composer update to fetch the latest versions of your dependencies in which this issue may have been resolved.