Use php 7 to run composer, but install packages for php 5

Question

I would like to run composer using php 7 installed inside a docker container, but the final software will run on php 5 since thats what the production server is running.

I don't see any correlation between installing software for php 5 and using php 7 cli to run composer, yet there appears to be a connection.

How can I tell composer that it doesn't matter what version I run composer with, what matters is the packages that it installs.

Answer 1

The correct solution it seems is to add the following

"config": {
    "platform": {
        "php": "5.6.17"
    }
}

to your composer file, then it will use that as the "version" of php you want to respect.

See https://getcomposer.org/doc/06-config.md#platform.