Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires doctrine/annotations 2.* -> satisfiable by doctrine/annotations[2.0.0, 2.0.1, 2.0.2]. - doctrine/annotations[2.0.0, ..., 2.0.2] require php ^7.2 || ^8.0 -> your php version (7.1.33) does not satisfy that requirement. Problem 2 - jms/serializer[1.0.0, ..., 1.1.0] require doctrine/annotations 1.* -> found doctrine/annotations[v1.0, ..., 1.14.4] but it conflicts with your root composer.json require (2.*). - jms/serializer[1.2.0, ..., 1.14.1] require doctrine/annotations ^1.0 -> found doctrine/annotations[v1.0, ..., 1.14.4] but it conflicts with your root composer.json require (2.*). - jms/serializer[2.0.0, ..., 2.3.0, 3.0.0, ..., 3.10.0] require php ^7.2 -> your php version (7.1.33) does not satisfy that requirement. - jms/serializer[3.11.0, ..., 3.28.0] require php ^7.2||^8.0 -> your php version (7.1.33) does not satisfy that requirement. - jms/serializer[3.29.0, ..., 3.29.1] require php ^7.2 || ^8.0 -> your php version (7.1.33) does not satisfy that requirement. - jms/serializer[3.30.0, ..., 3.32.5] require php ^7.4 || ^8.0 -> your php version (7.1.33) does not satisfy that requirement. - Root composer.json requires jms/serializer ^1 | ^2 | ^3 -> satisfiable by jms/serializer[1.0.0, ..., 1.14.1, 2.0.0, ..., 2.3.0, 3.0.0, ..., 3.32.5].