D:phpstudy_proWWW>composer selfupdate
Updating to version 2.0.8 (stable channel).
Downloading (100%)
Failed to decode response: zlib_decode(): data error
Retrying with degraded mode, check https://getcomposer.org/doc/a… for more info
起因 ：网络问题。
解决办法 **
composer 页提供了一个 degraded 模式的解决办法。如果咱们开启了 ipv6 则须要将 IPv6 勾销勾选。