Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires php ^7|^8 but your php version (5.3.29) does not satisfy that requirement. Problem 2 - guzzlehttp/psr7[1.1.0, ..., 1.9.1] require php >=5.4.0 -> your php version (5.3.29) does not satisfy that requirement. - Root composer.json requires guzzlehttp/psr7 ^1 -> satisfiable by guzzlehttp/psr7[1.0.0, ..., 1.9.1].