排查步骤 Steps:

1. ran composer self-update
2. ran composer diagnose and observed the following below  查看环境变量

Checking platform settings: OK

Checking git settings: OK

Checking http connectivity to packagist: OK

Checking https connectivity to packagist: OK

Checking github.com oauth access: OK

Checking disk free space: OK

Checking pubkeys: Tags Public Key Fingerprint: xxxxx

Dev Public Key Fingerprint: xxxxx

OK Checking composer version: OK

Composer version: 1.8.0

PHP version: 7.1.11

PHP binary path: C:\path\to\devdesktop\php7_1\php.exe

参考链接：https://drupal.stackexchange.com/questions/273342/your-php-version-does-not-satisfy-that-requirement

https://stackoverflow.com/questions/35538071/symfony2-composer-your-php-version-5-6-18-overriden-by-config-platform-php