Change and update requirements for a composer vendor package - composer-php

Question

I have a PHP project using composer. Among others there is this requirement:
/composer.json:
"require": {
.
.
"mypackage/backend": "^5.0",
.
.
}
mypackage/backend requires a third package:
/vendor/mypackage/backend/composer.json:
"require": {
.
.
"mypackage/pdf": "branch/name",
.
.
}
finaly mypackage/pdf requires a additional packages:
/vendor/mypackage/pdf/composer.json:
"require": {
"tecnickcom/tcpdf": "6.2.*",
"setasign/fpdi": "1.5.*",
"setasign/fpdi-tcpdf": "1.5.4"
}
I want mypackage/pdf to require the latest versions respectively, like this:
"require": {
"tecnickcom/tcpdf": "6.4.*",
"setasign/fpdi": "*",
"setasign/fpdi-tcpdf": "2.*"
}
So I want to do somethings like this:
composer require tecnickcom/tcpdf:6.4.4 setasign/fpdi-tcpdf:^2.3 setasign/fpdi:^2.3
but for the vendor package mypackage/pdf whithout to create another vendor folder in mypackage/pdf.
What is the composer way to do this?

Answer 1

Composer won't/You can't. Composer is a dependency manager (not a package manager), that means, for your main (the root) project, it will resolve all dependencies for a matching version.
That means it either can or there are conflicts and it can't.
Composer however will never install dependencies deeper inside the vendor folder than the first vendor/package-name hierarchy.
You have such a conflict in your example: "tecnickcom/tcpdf": "6.2.*" prevents "tecnickcom/tcpdf": "6.4.*" and vice-versa.
When you try to "install" this, the dependency will result in version conflict errors as there is no version of that package that will full-fil all of the two constraints: 6.2.* and 6.4.*.