laravel old version is not supporting php 8.0.8 - laravel

Question

I have installed php 8.0.8 on my local computer. Laravel new projects work perfect. But when I try to run Old projects it shows me error. When I try to run command
composer install
It gives me the error below:
Problem 1
- jeremy-dunn/php-fedex-api-wrapper is locked to version 5.0.1 and an update of this package was not requested.
- jeremy-dunn/php-fedex-api-wrapper 5.0.1 requires ext-soap * -> it is missing from your system. Install or enable PHP's soap extension.
To enable extensions, verify that they are enabled in your .ini files:
- C:\xampp\php\php.ini
You can also run `php --ini` inside terminal to see which files are used by PHP in CLI mode.
When I run:
composer dump-autoload
It shows this error:
Generating optimized autoload files Class App\Http\Controllers\Vendor\OrderController
located in C:/Users/Muhammad Adnan/Downloads/test-upwork-master/spree-retail/app\Http\Controllers\temp\OrderController.php does not comply with psr-4 autoloading standard. Skipping.
Class App\Http\Resources\profile\AddressesResponse located in C:/Users/Muhammad Adnan/Downloads/test-upwork-master/spree-retail/app\Http\Resources\Profile\AddressesResponse.php does not comply with psr-4 autoloading standard. Skipping.
Class Illuminate\Foundation\ComposerScripts is not autoloadable, can not call post-autoload-dump script
> #php artisan package:discover --ansi
Fatal error: Uncaught Error: Class "Illuminate\Foundation\Application" not found in C:\Users\Muhammad Adnan\Downloads\test-upwork-master\spree-retail\bootstrap\app.php:14
Stack trace:
#0 C:\Users\Muhammad Adnan\Downloads\test-upwork-master\spree-retail\artisan(20): require_once()
#1 {main}
thrown in C:\Users\Muhammad Adnan\Downloads\test-upwork-master\spree-retail\bootstrap\app.php on line 14
PHP Fatal error: Uncaught Error: Class "Illuminate\Foundation\Application" not found in C:\Users\Muhammad Adnan\Downloads\test-upwork-master\spree-retail\bootstrap\app.php:14
Stack trace:
#0 C:\Users\Muhammad Adnan\Downloads\test-upwork-master\spree-retail\artisan(20): require_once()
#1 {main}
thrown in C:\Users\Muhammad Adnan\Downloads\test-upwork-master\spree-retail\bootstrap\app.php on line 14
Script #php artisan package:discover --ansi handling the post-autoload-dump event returned with error code 255

Answer 1

Unfortunately, older versions of Laravel doesn't not support newer versions of PHP. Laravel 6 is the minimal version for PHP 8.0 support (and it is already pretty old from a web development perspective).
Of course, this is for a fresh installation, you might have code in your project that is also not PHP 8.0 compatible.
About this error:
Problem 1
- jeremy-dunn/php-fedex-api-wrapper is locked to version 5.0.1 and an update of this package was not requested.
- jeremy-dunn/php-fedex-api-wrapper 5.0.1 requires ext-soap * -> it is missing from your system. Install or enable PHP's soap extension.
The problem will be easy to fix, just install the soap extension. You seem on Windows so it should already installed but disabled.
You will have to uncomment ;extension=soap.dll in your php.ini file (or maybe in the ext directory located in your php directory, it depends).
There will probably be other extensions required but disabled, to get a full list execute composer check.
This is what is preventing composer from installing your dependencies (which lead Uncaught Error: Class "Illuminate\Foundation\Application" not found in to when you are calling composer dump-autoload).

Answer 2

I searched out and found a solution regarding this issue. Only single command is the solution
Note: Don't update composer.
composer install --ignore-platform-reqs