PHP精度解决方案

http://php.net/manual/zh/function.bcadd.php

上述网址中有对于精度的解决方案.

取一个数的精度,可以采用该数与0相加后取对应的精度的解决方案

如下

bcadd('1.23456789',0,5);

上面网址还有个笔记写的不错,是一个函数

在下面转一下该笔记

I made this to add an unlimited size of numbers together.. 

This could be useful for those without the BCMath extension. 

It allows decimals, and optional $Scale parameter.  If $Scale isn't specified, then it'll automatically adjust to show the correct number of decimals. 

<?php function Add($Num1,$Num2,$Scale=null) {   // check if they're valid positive numbers, extract the whole numbers and decimals   if(!preg_match("/^\+?(\d+)(\.\d+)?$/",$Num1,$Tmp1)||      !preg_match("/^\+?(\d+)(\.\d+)?$/",$Num2,$Tmp2)) return('0');   // this is where the result is stored   $Output=array();   // remove ending zeroes from decimals and remove point   $Dec1=isset($Tmp1[2])?rtrim(substr($Tmp1[2],1),'0'):'';   $Dec2=isset($Tmp2[2])?rtrim(substr($Tmp2[2],1),'0'):'';   // calculate the longest length of decimals   $DLen=max(strlen($Dec1),strlen($Dec2));   // if $Scale is null, automatically set it to the amount of decimal places for accuracy   if($Scale==null) $Scale=$DLen;   // remove leading zeroes and reverse the whole numbers, then append padded decimals on the end   $Num1=strrev(ltrim($Tmp1[1],'0').str_pad($Dec1,$DLen,'0'));   $Num2=strrev(ltrim($Tmp2[1],'0').str_pad($Dec2,$DLen,'0'));   // calculate the longest length we need to process   $MLen=max(strlen($Num1),strlen($Num2));   // pad the two numbers so they are of equal length (both equal to $MLen)   $Num1=str_pad($Num1,$MLen,'0');   $Num2=str_pad($Num2,$MLen,'0');   // process each digit, keep the ones, carry the tens (remainders)   for($i=0;$i<$MLen;$i++) {     $Sum=((int)$Num1{$i}+(int)$Num2{$i});     if(isset($Output[$i])) $Sum+=$Output[$i];     $Output[$i]=$Sum%10;     if($Sum>9) $Output[$i+1]=1;   }   // convert the array to string and reverse it   $Output=strrev(implode($Output));   // substring the decimal digits from the result, pad if necessary (if $Scale > amount of actual decimals)   // next, since actual zero values can cause a problem with the substring values, if so, just simply give '0'   // next, append the decimal value, if $Scale is defined, and return result   $Decimal=str_pad(substr($Output,-$DLen,$Scale),$Scale,'0');   $Output=(($MLen-$DLen<1)?'0':substr($Output,0,-$DLen));   $Output.=(($Scale>0)?".{$Decimal}":'');   return($Output); } $A="5650175242.508133742"; $B="308437806.831153821478770"; printf("  Add(%s,%s);\r\n// %s\r\n\r\n",$A,$B,  Add($A,$B)); printf("BCAdd(%s,%s);\r\n// %s\r\n\r\n",$A,$B,BCAdd($A,$B)); /*   This will produce the following..     Add(5650175242.508133742,308437806.831153821478770);   // 5958613049.33928756347877   BCAdd(5650175242.508133742,308437806.831153821478770);   // 5958613049 */ ?> 
It was a fun experience making, and thought I'd share it. 
Enjoy, 
Nitrogen.