在一台处理网络支付的服务器迁移的时候，发现不能支付。
1.php版本为5.3.3
2.系统为red hat 4.1.2-54
查看apache的错误日志，发现是加密文件中一个函数bcmul()报错：php fatal error:  call to undefined function bcmul() in /php_rsa.php on line xxx ,这个函数是php数学扩展中的一个,使用 bcscale() 来设置全局默认的小数位数，具体用法如下：

解决方法使用如下命令:yum install php-bcmath 就安装好了,如果出现下面这种情况：
loaded plugins: fastestmirror loading mirror speeds from cached hostfile * base: mirrors.yun-idc.com * extras: mirrors.yun-idc.com * rpmforge: ftp.riken.jp * updates: mirrors.yun-idc.com setting up install process resolving dependencies --> running transaction check ---> package php-bcmath.x86_64 0:5.1.6-40.el5_9 set to be updated --> processing dependency: php-common = 5.1.6-40.el5_9 for package: php-bcmath --> running transaction check ---> package php-common.x86_64 0:5.1.6-40.el5_9 set to be updated --> processing conflict: php53-common conflicts php-common --> finished dependency resolution php53-common-5.3.3-13.el5_9.1.x86_64 from installed has depsolving problems --> php53-common conflicts with php-common error: php53-common conflicts with php-common you could try using --skip-broken to work around the problem you could try running: package-cleanup --problems package-cleanup --dupes rpm -va --nofiles --nodigest
就需要使用yum update 之后再yum install php53-bcmath就好了,此函数在php.ini中的选项：
[bcmath] ; number of decimal digits for all bcmath functions. ; http://www.php.net/manual/en/bc.configuration.php#ini.bcmath.scale bcmath.scale = 0 bc //数学库配置选项
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