PHP 字符串替换后不能运算由于把公式写在数据库中：如 $gongshi="a+b+c";前台做替换如a=3；b=4;c=5;$gongshi=str_ireplace("3","a",$gongshi);$gongshi=str_ireplace("4","b",$gongshi);$gongshi=str_ireplace("5","c",$gongshi);替换成功3+4+5不能自动计算，该怎么办？ ------解决方案--------------------eval()
