一直安装不了webman，看下是什么原因？

我是按https://www.workerman.net/doc/webman#/install
这里的方案安装了 上面下面二个方法安装了都不行

提示的错误为以下：
第一：
data/wwwroot/webman# composer install
PHP Warning: require(Composer/autoload.php): failed to open stream: No such file or directory in /usr/bin/composer on line 9
PHP Fatal error: require(): Failed opening required 'Composer/autoload.php' (include_path='.:/usr/local/php/lib/php') in /usr/bin/composer on line 9

第二：
/data/wwwroot/webman# php start.php start
PHP Warning: require_once(/data/wwwroot/webman/vendor/autoload.php): failed to open stream: No such file or directory in /data/wwwroot/webman/start.php on line 2
PHP Fatal error: require_once(): Failed opening required '/data/wwwroot/webman/vendor/autoload.php' (include_path='.:/usr/local/php/lib/php') in /data/wwwroot/webman/start.php on line 2