The lock file is not up to date with the latest changes in composer.json
Run: composer update --lock to get your lock file in sync with your composer.json.
You may use depends & prohibits on composer to see what exactly you should do:
composer depends symfony/process 3.4.15and
composer prohibits symfony/symfony 4This two commands tell you what is the conflict and what you should do.
The main problem is that your composer.json and composer.lock are not in sync. The first file tells composer what are required package & their version constraints, and the second one shares the exact same package version between collaborators, for consistency.
If the repository owner does not help you with this problem, the only way you have is:
rm composer.lockrm -rf vendorcomposer installThis will remove vendor directory contents and install a fressh copy of all dependencies, according to just composer.json
share your comooser.json file please , i think you should update it :
"require": { "symfony/process": "3.4.*", "symfony/symfony": "3.4.*"},or
"require": { "symfony/process": "4.1.*", "symfony/symfony": "4.1.*"},