BC Math 函数
在线手册：中文 英文
PHP手册

bccomp

(PHP 4, PHP 5)

bccomp — Compare two arbitrary precision numbers

说明

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

Compares the left_operand to the right_operand and returns the result as an integer.

参数

left_operand

The left operand, as a string.

right_operand

The right operand, as a string.

scale

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

返回值

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

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

?>
BC Math 函数
在线手册：中文 英文
PHP手册
PHP手册 - N: Compare two arbitrary precision numbers

用户评论:

Robert Lozyniak (17-Feb-2010 06:04)

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

Nitrogen (21-Jul-2009 02:23)

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",$A,$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.

m dot kaczanowski at alianet dot pl (11-Mar-2009 02:35)

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 11:41)

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 10:03)

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);
   }
}
?>