部署环境 Apache/2.4.39 (Win64) PHP/7.1.29
php缺失必要的扩展 php-mbstring
可以直接百度搜索错误，看见很多解决方案
https://www.baidu.com/s?ie=utf-8&f=8&rsv_bp=1&tn=baidu&wd=Fatal%20error%3A%20Call%20to%20undefined%20function%20mb_substr()&oq=shopxo&rsv_pq=b7568b2d000d7ed9&rsv_t=0f5aiEnpUCQcUboD1MzKRtlxLP8jTkVFEboqMidf9rjLnoGm2WehEuRFVBg&rqlang=cn&rsv_enter=1&rsv_dl=tb&rsv_sug3=2&rsv_sug1=1&rsv_sug7=100&rsv_sug2=0&rsv_btype=t&inputT=818&rsv_sug4=826&rsv_sug=2
