Hướng dẫn bccomp trong php

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

bccomp — Compare two arbitrary precision numbers

Description

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

Parameters

The left operand, as a string.

The right operand, as a string.

The optional scale parameter is used to set the number of digits after the decimal place which will be used in the comparison.

Return Values

Returns 0 if the two operands are equal, 1 if the num1 is larger than the num2, -1 otherwise.

Changelog

Examples

Example #1 bccomp() example

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

Robert Lozyniak ¶

12 years ago

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

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

m dot kaczanowski at alianet dot pl ¶

13 years ago

Improvement of functions bcmax() and bcmin() originaly written by frank at booksku dot com

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

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:
function my_bccomp_zero($amount, $scale)
{
   if (@$amount{0}=="-")
   {
       return bccomp($amount, '-0.0', $scale);
   }
   else
   {
       return bccomp($amount, '0.0', $scale);
   }
}
?>

Nitrogen ¶

13 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.

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.

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.

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.

frank at booksku dot com ¶

17 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.

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

Artur Kuritsyn ¶

5 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