全局PHP安装包：apt-get vs composer

I found there are two options to install PHP package globally in Linux (Ubuntu 16.04):

1. Using composer:

   composer global require symfony/finder
   

   The package will be located at ~/.config/composer/vendor/

   

2. Using apt-get:

   apt-get install php-symfony-finder
   

   The package will be located at /usr/share/php/

   

   This directory /usr/share/php/ is also in default PHPs include_path (I have PHP 7.2)

   

There are several questions I have:

Why would I want to install package globally ?

I know it's useful to install php tools globally, like phpunit - It has binary file and it allows you to run tests everywhere, so you don't have to install it in every project. But what about symfony/finder for example ? What is particular use of this package installed globally ?

What is the difference between 1 and 2 option ?

Does it have any different use cases or different effects ?

Why would I want to install package globally ?

Normally, these are dependencies you want to use in almost every project, because they are available at a system level you can use them without duplicating their dependencies in every application you create.

For example, in my case I have php_md, php_cs for code formatting, phpunit for testing.

What is the difference between 1 and 2 option ?

Both are package managers, they make sure every package installed has the correct dependencies, so their core functionality is similar.

Now, they have several differences:

• Their focus in the packages they manage, composer is specific for php based packages but apt-get is for Linux and more system level oriented.
• Their package database, composer uses packagist and apt-get uses a selection of repositories and ppas (you can find them in /var/lib/apt/lists/).
• The package selection, since composer is specialized in php you can expect a wider variety in anything php related.

In conclusion, you can clearly make it work with both, but I would recommend you to keep everything php related on composer, unifying them under the same manager.

Any other difference or correction I've overlooked is welcome.