carbon 装不上，now () 函数用不了

Your requirements could not be resolved to an installable set of packages.

Problem 1

• laravel/framework v5.5.45 requires nesbot/carbon ^1.26.0 -> satisfiable by nesbot/carbon[1.26.0, 1.26.1, 1.26.2, 1.26.3, 1.26.4, 1.27.0, 1.28.0, 1.29.0, 1.29.1, 1.29.2, 1.30.0, 1.31.0, 1.31.1, 1.32.0, 1.33.0, 1.34.0, 1.34.1, 1.34.2, 1.34.3, 1.34.4, 1.35.0, 1.35.1, 1.36.0, 1.36.1, 1.36.2] but these conflict with your requirements or minimum-stability.

• Installation request for laravel/framework (locked at v5.5.45, required as 5.5.*) -> satisfiable by laravel/framework[v5.5.45].

Installation failed, reverting ./composer.json to its original content.