Composer

Backup your website: Before making any changes, it is essential to create a backup of your Magento 2 installation, including the database and files. This backup will serve as a safety net in case anything goes wrong during the update process.

Enable maintenance mode: Enable maintenance mode on your Magento 2 website. This will display a maintenance page to visitors while you perform the update, preventing any potential issues or disruptions.

to Force the composer to use a specific PHP version you can add this script to the composer.josn

	"config": {
		"optimize-autoloader": true,
		"prepend-autoloader": false,
		"platform": {
			"php": "8.0.13"
		}
	},

or you can use the command line to add it 

cd /path/to/project/dir
ls -l composer.json
composer config platform.php {PHP_VERSION_HERE}
composer config platform.php 8.x.x

to check all available versions of Magneto you can use this command

Magento Open Source:

composer show magento/product-community-edition --all | grep -m 1 versions

Magento Commerce:

composer show magento/product-enterprise-edition --all | grep -m 1 versions

Add artifact repository type into composer

to add an offline package and use it you can do the following 

{root}/vendor/{vendor}/packages

# composer config repositories.{your-name} artifact $(pwd)/vendor/{vendor}/packages 
# composer require {your-package}

You can use this command to update the composer into a specifc version 

composer self-update 1.4.1
 

The best way to check your files classes is to optimize the files using composer, here is a good command to do that

 php composer.phar update --no-dev --prefer-dist --no-interaction --optimize-autoloader --apcu-autoloader

Ignore PHP version using this command

--ignore-platform-reqs

you need to increase the memory_limit in php.ini

and as a quick solution you can use these commands directly in the command line

php -dmemory_limit=5G bin/magento setup:di:compile

and 

php -dmemory_limit=5G bin/magento setup:static-content:deploy

another code for the composer update

php -dmemory_limit=5G composer.phar update

php -d memory_limit=-1 /usr/local/bin/composer update
 

To install `package/module-name` with version `1.1.*` and minimum stability `@dev` use this:

php composer.phar require package/module-name:1.1.*@dev

then to update only this single package:

php composer.phar update package/module-name

you can use "--ignore-platform-reqs" to ignore installing the dependencies