[Composer\Downloader\TransportException]
Your configuration does not allow connections to http://packagist.phpcompos
er.com/packages.json. See https://getcomposer.org/doc/06-config.md#secure-h
ttp for details.

这个问题，其实是composer 默认走https 所以你需要关闭这个https的选项。

composer config secure-http false

或者编辑你的composer.json文件，添加如下行

"config": {
    "secure-http": false
}