我没有使用 docker-php-ext-install ，这是在容器中添加工作时必需的...

I wasn't using docker-php-ext-install which is required when adding working within the container...

FROM php:7-fpm-alpine

# install extensions needed for Laravel
RUN apk update \
    && apk add libmcrypt-dev \
    && docker-php-ext-install mcrypt mysqli pdo_mysql \
    && rm /var/cache/apk/*