php教程

bccomp

(PHP 4, PHP 5, PHP 7)

bccomp比较两个任意精度的数字

说明

bccomp ( string $left_operand , string $right_operand [, int $scale = int ] ) : int

right_operandleft_operand作比较, 并且返回一个整数的结果.

参数

left_operand

左边的运算数, 是一个字符串.

right_operand

右边的运算数, 是一个字符串.

scale

可选的scale参数被用作设置指示数字, 在使用来作比较的小数点部分.

返回值

如果两个数相等返回0, 左边的数left_operand比较右边的数right_operand大返回1, 否则返回-1.

范例

Example #1 bccomp() example

<?php

echo bccomp('1''2') . "\n";   // -1
echo bccomp('1.00001''1'3); // 0
echo bccomp('1.00001''1'5); // 1

?>

User Contributed Notes

aaugrin at gmail dot com 19-Feb-2018 10:01
BEWARE! left and right operand is string!! so number in E-notation like 9.012E-6  need to be converted with sprintf('%F') to string
Artur Kuritsyn 18-Sep-2017 11:57
bccomp - doesn't compare by default more then 16 characters

$number = '-4.444444444444444444444444444444444444444444445';
$precision = 16;
var_dump(bccomp(bcadd($number, '0', $precision), bcadd($number, '0', $precision+1)));

//outputs 0 on PHP 5.3

use strcomp
simonrataj at seznam dot cz 28-Jun-2016 03:26
In PHP 7, bccomp($a, $b) is the same as $a <=> $b.
github.com/alixaxel/phunction/ 07-May-2012 01:19
You can wrap this function with version_compare() to have support for operators and friendlier (boolean) return values.

<?php

function _bccomp($a, $b, $operator = '=')
{
    return
version_compare(bccomp($a, $b), 0, $operator);
}

var_dump(_bccomp(5, 3, '>=')); // true

?>

Still works with arbitrary length numbers.
Robert Lozyniak 16-Feb-2010 10:04
Beware that negative zero does not compare equal to positive zero.
Nitrogen 21-Jul-2009 06:23
I made this to compare an unlimited size of numbers..

This could be useful for those without the BCMath extension.

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

<?php

function Comp($Num1,$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');

 
// remove leading zeroes from whole numbers
 
$Num1=ltrim($Tmp1[1],'0');
 
$Num2=ltrim($Tmp2[1],'0');

 
// first, we can just check the lengths of the numbers, this can help save processing time
  // if $Num1 is longer than $Num2, return 1.. vice versa with the next step.
 
if(strlen($Num1)>strlen($Num2)) return(1);
  else {
    if(
strlen($Num1)<strlen($Num2)) return(-1);

   
// if the two numbers are of equal length, we check digit-by-digit
   
else {

     
// 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'):'';

     
// if the user defined $Scale, then make sure we use that only
     
if($Scale!=null) {
       
$Dec1=substr($Dec1,0,$Scale);
       
$Dec2=substr($Dec2,0,$Scale);
      }

     
// calculate the longest length of decimals
     
$DLen=max(strlen($Dec1),strlen($Dec2));

     
// append the padded decimals onto the end of the whole numbers
     
$Num1.=str_pad($Dec1,$DLen,'0');
     
$Num2.=str_pad($Dec2,$DLen,'0');

     
// check digit-by-digit, if they have a difference, return 1 or -1 (greater/lower than)
     
for($i=0;$i<strlen($Num1);$i++) {
        if((int)
$Num1{$i}>(int)$Num2{$i}) return(1);
        else
          if((int)
$Num1{$i}<(int)$Num2{$i}) return(-1);
      }

     
// if the two numbers have no difference (they're the same).. return 0
     
return(0);
    }
  }
}

$A="10.50002";
$B="10.50001";

printf("  Comp(%s,%s); // %s\r\n",$A,$BComp($A,$B));
printf("BCComp(%s,%s); // %s\r\n",$A,$B,BCComp($A,$B));

/*
    Comp(10.50002,10.50001); // 1
  BCComp(10.50002,10.50001); // 0 (BCComp has a default decimal scale of 0, unless specified)
*/

?>

I tried to make this behave like BCComp..

The only difference being mine will compare the decimals by default.. BCComp won't..
.. unless, of course, you specify the amount of decimals to include in the process.
Enjoy,
Nitrogen.
m dot kaczanowski at alianet dot pl 11-Mar-2009 06:35
Improvement of functions bcmax() and bcmin() originaly written by frank at booksku dot com

<?php

function bcmax() {
 
$args = func_get_args();
  if (
count($args)==0) return false;
 
$max = $args[0];
  foreach(
$args as $value) {
    if (
bccomp($value, $max)==1) {
     
$max = $value;
    }
  }
  return
$max;
}

function
bcmin() {
 
$args = func_get_args();
  if (
count($args)==0) return false;
 
$min = $args[0];
  foreach(
$args as $value) {
    if (
bccomp($min, $value)==1) {
     
$min = $value;
    }
  }
  return
$min;
}
?>
frank at booksku dot com 04-Oct-2005 03:41
I slapped together min() and max() functions using bccomp().  While min() and max() only take an arbitrary number of args (i.e. max(1, 5, 1235, 12934, 66)) bccomp only takes 2.

Note that this doesn't take into account $scale.

<?php

function bcmax() {
 
$max = null;
  foreach(
func_get_args() as $value) {
    if (
$max == null) {
     
$max = $value;
    } else if (
bccomp($max, $value) < 0) {
     
$max = $value;
    }
  }
  return
$max;
}

function
bcmin() {
 
$min = null;
  foreach(
func_get_args() as $value) {
    if (
$min == null) {
     
$min = $value;
    } else if (
bccomp($min, $value) > 0) {
     
$min = $value;
    }
  }
  return
$min;
}
?>
11-Feb-2005 02:03
Note that the above function defeats the purpose of BCMath functions, for it uses the 'conventional' < operator.
Instead, it should be:
<?php
function my_bccomp_zero($amount, $scale)
{
   if (@
$amount{0}=="-")
   {
       return
bccomp($amount, '-0.0', $scale);
   }
   else
   {
       return
bccomp($amount, '0.0', $scale);
   }
}
?>

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