These functions DO NOT round off your values. No arbitrary precision libraries do it this way. It stops calculating after reaching scale of decimal places, which mean that your value is cut off after scale number of digits, not rounded. To do the rounding use something like this:
<?php
function bcround($number, $scale=0) {
$fix = "5";
for ($i=0;$i<$scale;$i++) $fix="0$fix";
$number = bcadd($number, "0.$fix", $scale+1);
return bcdiv($number, "1.0", $scale);
}
?>
bcscale
(PHP 4, PHP 5)
bcscale — Setzt die Genauigkeit aller BCmath-Funktionen
Beschreibung
bool bcscale
( int
$scale
)Diese Funktionen legt die Standard-Genauigkeit aller im Folgenden aufgerufenden BCmath-Funktionen fest, die nicht explizit die Genauigkeit angeben.
Parameter-Liste
-
scale -
Die Genauigkeitsangabe.
Rückgabewerte
Gibt bei Erfolg TRUE zurück. Im Fehlerfall wird FALSE zurückgegeben.
Beispiele
Beispiel #1 bcscale()-Beispiel
<?php
// Standard-Genauigkeit: 3
bcscale(3);
echo bcdiv('105', '6.55957'); // 16.007
// Die selbe Operation ohne Verwendung von bcscale()
echo bcdiv('105', '6.55957', 3); // 16.007
?>
add a note
User Contributed Notes 6 notes
mwgamera at gmail dot com ¶
6 years ago
herslyadam at gmail dot com ¶
3 months ago
edited bcround function with negative number support:
<?php
function bcround($number, $scale=0) {
if($scale < 0) $scale = 0;
$sign = '';
if(bccomp('0', $number, 64) == 1) $sign = '-';
$increment = $sign . '0.' . str_repeat('0', $scale) . '5';
$number = bcadd($number, $increment, $scale+1);
return bcadd($number, '0', $scale);
}
?>
admin at torntech dot com ¶
2 days ago
Keep in mind that the documentation states "all subsequent calls to bc math functions" and should be handled as if changing a global PHP ini setting via ini_set. This applies to object instantiation as well and will not reset after the object is no longer in use as would normally be expected.
<?php
class foo
{
public function __construct()
{
\bcscale(5);
new bar;
}
}
class bar
{
public function __construct()
{
\var_dump(\bcadd('1', '2'));
}
}
new bar; //string(1) "3"
$foo = new foo; //string(7) "3.00000"
unset($foo); //disposal of object
new bar; //string(7) "3.00000"
?>
ravenswd at gmail dot com ¶
2 years ago
Simple, easy way to remove excess trailing zeros using rtrim:
<php>
// $total is the result of a bcmath calculation
if ( strpos($total, '.') !== false ):
$total = rtrim($total, '0');
$total = rtrim($total, '.');
endif;
</php>
rastislav dot bostik at bwd21 dot cz ¶
2 years ago
Previously stated one liner trailing 0 removing using rtrim() works fine except following class of subcases:
<?php
echo rtrim('100.0000', '0.'); // 1 instead 100
echo rtrim('1230.00000000', '0.'); // 123 instead 1230
?>
What seems to be working to me is using regular expression replacement. Althought it`s probably not that fast as rtrim(), I hope it should be more reliable:
<?php
function removeFloatNumStringZeroTrailer($input) {
$patterns = array('/[\.][0]+$/','/([\.][0-9]*[1-9])([0]*)$/');
$replaces = array('','$1');
return preg_replace($patterns,$replaces,$input);
}
echo removeFloatNumStringZeroTrailer('100.0000'); // says 100
echo removeFloatNumStringZeroTrailer('1230.00000000'); // says 1230
?>
invincible at limitedintelligence dot com ¶
8 years ago
If you don't set the default scale, be careful when you're chaining together several BC math functions - since by default, these functions will round off your values, losing accuracy very quickly:
<?php
$a = 1.234
$b = 2.345
$c = 7.890
$ab = bcmul($a,$b); // 2
$abc = bcmul($ab,$c);
echo $abc; // 15
?>
... compare with the answer you get when you use more decimal places:
<?php
$a = 1.234
$b = 2.345
$c = 7.890
bcscale(15);
$ab = bcmul($a,$b); // 2.893730
$abc = bcmul($ab,$c);
echo $abc; // 22.83152970
?>
