Root composer.json requires webman/admin ^2.1 -> satisfiable by webman/admin[v2.1.1].
webman/admin v2.1.1 requires workerman/webman-framework >=2.1 -> found workerman/webman-framework[dev-master, v2.1.0, v2.1.1] but it conflicts with your root composer.json require (^1.5.0).
You can also try re-running composer require with an explicit version constraint, e.g. "composer require webman/admin:*" to figure out if any version is installable, or "composer require webman/admin:^2.1" if you know which you need.
webman1.x 执行
composer require -W webman/admin ^1.0