(PHP 4, PHP 5, PHP 7, PHP 8)
round — Rounds a float
$num, int $precision = 0, int|RoundingMode $mode = RoundingMode::HalfAwayFromZero): float
Returns the rounded value of num to
specified precision
(number of digits after the decimal point).
precision can also be negative or zero (default).
numThe value to round.
precisionThe optional number of decimal digits to round to.
If the precision is positive, num is
rounded to precision significant digits after the decimal point.
If the precision is negative, num is
rounded to precision significant digits before the decimal point,
i.e. to the nearest multiple of pow(10, -$precision), e.g. for a
precision of -1 num is rounded to tens,
for a precision of -2 to hundreds, etc.
modeUse RoundingMode or one of the following constants to specify the mode in which rounding occurs.
| Constants | Description |
|---|---|
PHP_ROUND_HALF_UP |
Rounds num away from zero when it is half way there,
making 1.5 into 2 and -1.5 into -2.
|
PHP_ROUND_HALF_DOWN |
Rounds num towards zero when it is half way there,
making 1.5 into 1 and -1.5 into -1.
|
PHP_ROUND_HALF_EVEN |
Rounds num towards the nearest even value when it is half way
there, making both 1.5 and 2.5 into 2.
|
PHP_ROUND_HALF_ODD |
Rounds num towards the nearest odd value when it is half way
there, making 1.5 into 1 and 2.5 into 3.
|
The function throws a ValueError if mode is
invalid.
Prior to PHP 8.4.0, an invalid mode would silently default to PHP_ROUND_HALF_UP.
| Version | Description |
|---|---|
| 8.4.0 | Four new rounding modes have been added. |
| 8.4.0 |
Now throws a ValueError if
mode is invalid.
|
| 8.0.0 |
num no longer accepts internal objects which support
numeric conversion.
|
Example #1 round() examples
<?php
var_dump(round(3.4));
var_dump(round(3.5));
var_dump(round(3.6));
var_dump(round(3.6, 0));
var_dump(round(5.045, 2));
var_dump(round(5.055, 2));
var_dump(round(345, -2));
var_dump(round(345, -3));
var_dump(round(678, -2));
var_dump(round(678, -3));
?>The above example will output:
float(3) float(4) float(4) float(4) float(5.05) float(5.06) float(300) float(0) float(700) float(1000)
Example #2 How precision affects a float
<?php
$number = 135.79;
var_dump(round($number, 3));
var_dump(round($number, 2));
var_dump(round($number, 1));
var_dump(round($number, 0));
var_dump(round($number, -1));
var_dump(round($number, -2));
var_dump(round($number, -3));
?>The above example will output:
float(135.79) float(135.79) float(135.8) float(136) float(140) float(100) float(0)
Example #3 mode examples
<?php
echo 'Rounding modes with 9.5' . PHP_EOL;
var_dump(round(9.5, 0, PHP_ROUND_HALF_UP));
var_dump(round(9.5, 0, PHP_ROUND_HALF_DOWN));
var_dump(round(9.5, 0, PHP_ROUND_HALF_EVEN));
var_dump(round(9.5, 0, PHP_ROUND_HALF_ODD));
echo PHP_EOL;
echo 'Rounding modes with 8.5' . PHP_EOL;
var_dump(round(8.5, 0, PHP_ROUND_HALF_UP));
var_dump(round(8.5, 0, PHP_ROUND_HALF_DOWN));
var_dump(round(8.5, 0, PHP_ROUND_HALF_EVEN));
var_dump(round(8.5, 0, PHP_ROUND_HALF_ODD));
?>The above example will output:
Rounding modes with 9.5 float(10) float(9) float(10) float(9) Rounding modes with 8.5 float(9) float(8) float(8) float(9)
Example #4 mode with precision examples
<?php
echo 'Using PHP_ROUND_HALF_UP with 1 decimal digit precision' . PHP_EOL;
var_dump(round( 1.55, 1, PHP_ROUND_HALF_UP));
var_dump(round(-1.55, 1, PHP_ROUND_HALF_UP));
echo PHP_EOL;
echo 'Using PHP_ROUND_HALF_DOWN with 1 decimal digit precision' . PHP_EOL;
var_dump(round( 1.55, 1, PHP_ROUND_HALF_DOWN));
var_dump(round(-1.55, 1, PHP_ROUND_HALF_DOWN));
echo PHP_EOL;
echo 'Using PHP_ROUND_HALF_EVEN with 1 decimal digit precision' . PHP_EOL;
var_dump(round( 1.55, 1, PHP_ROUND_HALF_EVEN));
var_dump(round(-1.55, 1, PHP_ROUND_HALF_EVEN));
echo PHP_EOL;
echo 'Using PHP_ROUND_HALF_ODD with 1 decimal digit precision' . PHP_EOL;
var_dump(round( 1.55, 1, PHP_ROUND_HALF_ODD));
var_dump(round(-1.55, 1, PHP_ROUND_HALF_ODD));
?>The above example will output:
Using PHP_ROUND_HALF_UP with 1 decimal digit precision float(1.6) float(-1.6) Using PHP_ROUND_HALF_DOWN with 1 decimal digit precision float(1.5) float(-1.5) Using PHP_ROUND_HALF_EVEN with 1 decimal digit precision float(1.6) float(-1.6) Using PHP_ROUND_HALF_ODD with 1 decimal digit precision float(1.5) float(-1.5)
Example #5 Example of using RoundingMode
<?php
foreach (RoundingMode::cases() as $mode) {
foreach ([
8.5,
9.5,
-3.5,
] as $number) {
printf("%-17s: %+.17g -> %+.17g\n", $mode->name, $number, round($number, 0, $mode));
}
echo "\n";
}
?>The above example will output:
HalfAwayFromZero : +8.5 -> +9 HalfAwayFromZero : +9.5 -> +10 HalfAwayFromZero : -3.5 -> -4 HalfTowardsZero : +8.5 -> +8 HalfTowardsZero : +9.5 -> +9 HalfTowardsZero : -3.5 -> -3 HalfEven : +8.5 -> +8 HalfEven : +9.5 -> +10 HalfEven : -3.5 -> -4 HalfOdd : +8.5 -> +9 HalfOdd : +9.5 -> +9 HalfOdd : -3.5 -> -3 TowardsZero : +8.5 -> +8 TowardsZero : +9.5 -> +9 TowardsZero : -3.5 -> -3 AwayFromZero : +8.5 -> +9 AwayFromZero : +9.5 -> +10 AwayFromZero : -3.5 -> -4 NegativeInfinity : +8.5 -> +8 NegativeInfinity : +9.5 -> +9 NegativeInfinity : -3.5 -> -4 PositiveInfinity : +8.5 -> +9 PositiveInfinity : +9.5 -> +10 PositiveInfinity : -3.5 -> -3
In my opinion this function lacks two flags:
- PHP_ROUND_UP - Always round up.
- PHP_ROUND_DOWN - Always round down.
In accounting, it's often necessary to always round up, or down to a precision of thousandths.
<?php
function round_up($number, $precision = 2)
{
$fig = (int) str_pad('1', $precision, '0');
return (ceil($number * $fig) / $fig);
}
function round_down($number, $precision = 2)
{
$fig = (int) str_pad('1', $precision, '0');
return (floor($number * $fig) / $fig);
}
?>As PHP doesn't have a a native number truncate function, this is my solution - a function that can be usefull if you need truncate instead round a number.
<?php
/**
* Truncate a float number, example: <code>truncate(-1.49999, 2); // returns -1.49
* truncate(.49999, 3); // returns 0.499
* </code>
* @param float $val Float number to be truncate
* @param int f Number of precision
* @return float
*/
function truncate($val, $f="0")
{
if(($p = strpos($val, '.')) !== false) {
$val = floatval(substr($val, 0, $p + 1 + $f));
}
return $val;
}
?>
Originally posted in http://stackoverflow.com/a/12710283/1596489If you have negative zero and you need return positive number simple add +0:
$number = -2.38419e-07;
var_dump(round($number,1));//float(-0)
var_dump(round($number,1) + 0);//float(0)I discovered that under some conditions you can get rounding errors with round when converting the number to a string afterwards.
To fix this I swapped round() for number_format().
Unfortunately i cant give an example (because the number cant be represented as a string !)
essentially I had round(0.688888889,2);
which would stay as 0.68888889 when printed as a string.
But using number_format it correctly became 0.69.Unexpected result or misunderstanding (php v5.5.9)
<?php
echo round(1.55, 1, PHP_ROUND_HALF_DOWN); // 1.5
echo round(1.551, 1, PHP_ROUND_HALF_DOWN); //1.6
?>function mround($val, $f=2, $d=6){
return sprintf("%".$d.".".$f."f", $val);
}
echo mround(34.89999); //34.90If you'd only want to round for displaying variables (not for calculating on the rounded result) then you should use printf with the float:
<?php printf ("%6.2f",3.39532); ?>
This returns: 3.40 .Here is function that rounds to a specified increment, but always up. I had to use it for price adjustment that always went up to $5 increments.
<?php
function roundUpTo($number, $increments) {
$increments = 1 / $increments;
return (ceil($number * $increments) / $increments);
}
?>this function (as all mathematical operators) takes care of the setlocale setting, resulting in some weirdness when using the result where the english math notation is expected, as the printout of the result in a width: style attribute!
<?php
$a=3/4;
echo round($a, 2); // 0.75
setlocale(LC_ALL, 'it_IT@euro', 'it_IT', 'it');
$b=3/4;
echo round($b,2); // 0,75
?>This function will let you round to an arbitrary non-zero number. Zero of course causes a division by zero.
<?php
function roundTo($number, $to){
return round($number/$to, 0)* $to;
}
echo roundTo(87.23, 20); //80
echo roundTo(-87.23, 20); //-80
echo roundTo(87.23, .25); //87.25
echo roundTo(.23, .25); //.25
?>/**
* Round to first significant digit
* +N to +infinity
* -N to -infinity
*
*/
function round1stSignificant ( $N ) {
if ( $N === 0 ) {
return 0;
}
$x = floor ( log10 ( abs( $N ) ) );
return ( $N > 0 )
? ceil( $N * pow ( 10, $x * -1 ) ) * pow( 10, $x )
: floor( $N * pow ( 10, $x * -1 ) ) * pow( 10, $x );
}
echo round1stSignificant( 39144818 ) . PHP_EOL;
echo round1stSignificant( 124818 ) . PHP_EOL;
echo round1stSignificant( 0.07468 ) . PHP_EOL;
echo round1stSignificant( 0 ) . PHP_EOL;
echo round1stSignificant( -0.07468 ) . PHP_EOL;
/**
* Output
*
* 40000000
* 200000
* 0.08
* 0
* -0.08
*
*/Here's a function to round to an arbitary number of significant digits. Don't confuse it with rounding to a negative precision - that counts back from the decimal point, this function counts forward from the Most Significant Digit.
ex:
<?php
round(1241757, -3); // 1242000
RoundSigDigs(1241757, 3); // 1240000
?>
Works on negative numbers too. $sigdigs should be >= 0
<?php
function RoundSigDigs($number, $sigdigs) {
$multiplier = 1;
while ($number < 0.1) {
$number *= 10;
$multiplier /= 10;
}
while ($number >= 1) {
$number /= 10;
$multiplier *= 10;
}
return round($number, $sigdigs) * $multiplier;
}
?>round() will sometimes return E notation when rounding a float when the amount is small enough - see https://bugs.php.net/bug.php?id=44223 . Apparently it's a feature.
To work around this "feature" when converting to a string, surround your round statement with an sprintf:
sprintf("%.10f", round( $amountToBeRounded, 10));