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round

PHP function Edit on GitHub ✎

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

Rounds a float

Description

round(int|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).

Parameters

num

The value to round.

precision

The 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.

mode

Use RoundingMode or one of the following constants to specify the mode in which rounding occurs.

ConstantsDescription
PHP_ROUND_HALF_UPRounds num away from zero when it is half way there, making 1.5 into 2 and -1.5 into -2.
PHP_ROUND_HALF_DOWNRounds num towards zero when it is half way there, making 1.5 into 1 and -1.5 into -1.
PHP_ROUND_HALF_EVENRounds num towards the nearest even value when it is half way there, making both 1.5 and 2.5 into 2.
PHP_ROUND_HALF_ODDRounds num towards the nearest odd value when it is half way there, making 1.5 into 1 and 2.5 into 3.

However, please note that some newly added modes only exist in RoundingMode.

Return Values

The value rounded to the given precision as a Float.

Errors/Exceptions

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.

Changelog

VersionDescription
8.4.0Four new rounding modes have been added.
8.4.0Now throws a ValueError if mode is invalid.
8.0.0num no longer accepts internal objects which support numeric conversion.

Examples

round() examples

php
<?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:

output
float(3)
float(4)
float(4)
float(4)
float(5.05)
float(5.06)
float(300)
float(0)
float(700)
float(1000)

How precision affects a float

php
<?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:

output
float(135.79)
float(135.79)
float(135.8)
float(136)
float(140)
float(100)
float(0)

mode examples

php
<?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:

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)

mode with precision examples

php
<?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:

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 of using RoundingMode

php
<?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:

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

See Also

Source: reference/math/functions/round.xml · from the official PHP manual (php/doc-en)