PHP - Manual: bccomp

2024-11-14

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bccomp

(PHP 4, PHP 5, PHP 7, PHP 8)

bccomp — 比较两个任意精度的数字

说明

bccomp(string $num1, string $num2, ?int $scale = null): int

比较 num1 和 num2, 并且返回整型数字的结果。

参数

num1: 左边的运算数，是一个字符串。
num2: 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

两个数相等时返回 0； num1 比 num2 大时返回 1；其他则返回 -1。

更新日志

版本	说明
8.0.0	现在 `scale` 可以为 null。

范例

示例 #1 bccomp() 示例


<?php

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

?>

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User Contributed Notes 9 notes

down

Robert Lozyniak ¶

12 years ago


Beware that negative zero does not compare equal to positive zero.

down

aaugrin at gmail dot com ¶

4 years ago


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

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-6

m dot kaczanowski at alianet dot pl ¶

13 years ago


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;
}
?>

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-9

Anonymous ¶

17 years ago


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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-10

Nitrogen ¶

12 years ago


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",$A,$B,  Comp($A,$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.

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-10

github.com/alixaxel/phunction/ ¶

10 years ago


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.

down

-7

frank at booksku dot com ¶

16 years ago


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;
}
?>

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-9

Artur Kuritsyn ¶

4 years ago


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

down

-15

simonrataj at seznam dot cz ¶

5 years ago


In PHP 7, bccomp($a, $b) is the same as $a <=> $b.

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官方地址：https://www.php.net/manual/en/function.bccomp.php

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PHP官方手册 - 互联网笔记

bccomp

说明

参数

返回值

更新日志

范例

User Contributed Notes 9 notes