Composer Akeneo installation Could not open input file composer.phar - apache

Question

I am trying to install a PIM named Akeneo. The system requirements are all checked:
https://docs.akeneo.com/2.3/install_pim/manual/system_requirements/system_requirements.html
I am on Apache2 / Ubuntu 16.04
My /var/www/ directory all belongs to www-data:www-data ( ran chown -R www-data:www-data to install )
Error message from server : “Could not open input file: composer.phar”
Googled about it , got many results, and looked on the forums on stakoverflow, found answers from 2010 to 2018. I think I have maybe found out that the problem could be linked with the file "composer.phar", the way symlinks work on apache2, and composer installed globally or "inside individual project(s)".
Following 2 tutorials, I had to install composer to continue the install for that PIM.
My server says:
Composer (version 1.10.10) successfully installed to:
/usr/local/bin/composer
If I navigate to cd ~ and run ls I see there is "composer.phar" and "composer-setup.php" here.
I am confused because the Akeno tutorial says:
After extracting the file, change into the Akeneo directory and run
the commands below:
cd /var/www/html/akeneo/pim-community-standard
sudo php -d memory_limit=3G ../composer.phar install --optimize-autoloader --prefer-dist
sudo php bin/console cache:clear --no-warmup --env=prod
...
I don't understand the composer.phar install part . There are no composer.phar file inside any directories : not in /var/www/html/akeneo/ and not in /var/www/html/akeneo/pim-community-standard
Was it supposed to generate a composer.phar file there ? Should it find composer.phar one level above ( ../composer.phar ) ? I doubled checked the Akeneo PIM files , and the original .rar archive has no composer.phar file. Or, is it something to do with a symlink that accesses the global "composer.phar" which was with the global install ? Regarding symlinks, there are some in the "vendor" fodler of the PIM, and runing ls -l -a gives :
lrwxrwxrwx 1 www-data www-data 28 Feb 5 2020 doctrine -> ../doctrine/orm/bin/doctrine
lrwxrwxrwx 1 www-data www-data 34 Feb 5 2020 doctrine-dbal -> ../doctrine/dbal/bin/doctrine-dbal
lrwxrwxrwx 1 www-data www-data 46 Feb 5 2020 doctrine-migrations -> ../doctrine/migrations/bin/doctrine-migrations
lrwxrwxrwx 1 www-data www-data 56 Feb 5 2020 requirements-checker -> ../symfony/requirements-checker/bin/requirements-checker
lrwxrwxrwx 1 www-data www-data 51 Feb 5 2020 var-dump-server -> ../symfony/var-dumper/Resources/bin/var-dump-server
There is a composer.json and composer.lock file inside /var/www/html/akeneo/pim-community-standard . So confused because the turorial says to be inside pim-community-standard directory and run this : php -d memory_limit=3G ../composer.phar install --optimize-autoloader --prefer-dist
I hope I can resume the install without breaking anything. Some posts give the solution of updating composer, or installing composer-phar, inside the project. I am honestly totally lost.
( I don't know if I should bring that up, but is docker needed (not talked about in tutorial - but I see a folder with "docker" in it and I know that composer and docker can work together sometimes )

Answer 1

I moved the composer.phar file into the app directory. Now the install advanced. It's not a technical issue a misconfiguration or anything like that.
It's a lack of information about Composer on the Akeneo site but it's probably assumed that users should have knowledge about Composer allready.
Solution for me : moving the "composer.phar" file (from 'home' for me ) to the /var/www/project/ (.. the correct level directory).
So for my case it was a global / local install issue , which is still unclear, and I will have to look deeper how to properly install composer. Not sure if my current setup will not cause any issue later since it's like I installed it globally at first then moved only one file.
Also, command "composer" is not returning anything. I do have the composer file in /usr/bin/ though. This is very strange.