安装PHP的BC扩展时，报的错。
使用的命令为
yum install php-bcmath
输出错误：
--> Processing Conflict: php72w-common-7.2.19-1.w7.x86_64 conflicts php-common < 7.2
--> Finished Dependency Resolution
Error: php72w-common conflicts with php-common-5.4.16-46.el7.x86_64
You could try using --skip-broken to work around the problem
You could try running: rpm -Va --nofiles --nodigest
更改命令为：
yum install php72w-bcmath
搞定
