change symfony 5 php version on debian code example

Example 1: symfony install website skeleton

# run this if you are building a traditional web application
 composer create-project symfony/website-skeleton my_project_name

Example 2: symfony new project

# use the most recent LTS version
$ symfony new my_project_name --version=lts

# use the 'next' Symfony version to be released (still in development)
$ symfony new my_project_name --version=next

# you can also select an exact specific Symfony version
$ symfony new my_project_name --version=4.4

# The --full option installs all the packages that you usually need to build web applications.