PHP中Call to undefined function mb_substr()处理方法
PHP中Call to undefined function mb_substr()处理方法！
最近开发微信扩展功能，用到了mb_substr()函数。系统在windows下测试都是正常的，但是放到aliyun（选用的Centos系统）下面就出现了问题，Call to undefined function mb_substr()，报出这个异常。
很显然，这是调用了没有定义的函数，可是环境都采用yum安装的，Apache和PHP都是自动安装的。怎么会出现这个错误呢？其实PHP本身也是可配置的，安装时候除了必须的扩展库会自动安装上之外，其他的库默认是不会安装的。
解决办法：
yum install php-mbstring 命令安装，安装好后 service httpd restart 重启apache服务器，一切正常！
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