Phenomenon: the following tips when using the composer intended conditions install plug-ins:
1.content-length mismatch
2. composer http://packagist.org could not be fully loaded
The reason
: A possible reason is that the installation package URL composer's foreign image caused by the Great Firewall blocked. Execute the following command to resolve:
1. Modify for domestic mirror
（1） composer config -g repo.packagist composer https://packagist.phpcomposer.com
（2）阿里云镜像：composer config -g repo.packagist composer https://mirrors.aliyun.com/composer/
2. Re-load plugins php composer.phar require --prefer-dist plugin name