PHP FATAL ERROR: CALL TO UNDEFINED FUNCTION BCMUL()解决办法

在一台处理网络支付的服务器迁移的时候，发现不能支付。

PHP环境：
PHP版本为5.3.3
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

解决办法：
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

顺便了解了一下，bcmath这个函数是PHP数学扩展中的一个。可以使用 bcscale() 来设置全局默认的小数位数，具体用法如下：

string bcmul ( string $left_operand , string $right_operand [, int $scale ] )

例子：

<?php
echo bcmul('1.34747474747', '35', 3); // 47.161
echo bcmul('2', '4'); // 8
?>

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