round

(PHP 4, PHP 5, PHP 7)

round — Rounds a float

Description

round ( float $val [, int $precision = 0 [, int $mode = PHP_ROUND_HALF_UP ]] ) : float

Returns the rounded value of val to specified precision (number of digits after the decimal point). precision can also be negative or zero (default).

Note: PHP doesn't handle strings like "12,300.2" correctly by default. See converting from strings.

Parameters

val

The value to round.

precision

The optional number of decimal digits to round to.

If the precision is positive, val is rounded to precision significant digits after the decimal point.

If the precision is negative, val 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 val is rounded to tens, for a precision of -2 to hundreds, etc.

mode

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

Constants Description
PHP_ROUND_HALF_UP Rounds val away from zero when it is half way there, making 1.5 into 2 and -1.5 into -2.
PHP_ROUND_HALF_DOWN Rounds val towards zero when it is half way there, making 1.5 into 1 and -1.5 into -1.
PHP_ROUND_HALF_EVEN Rounds val 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 val towards the nearest odd value when it is half way there, making 1.5 into 1 and and 2.5 into 3.

Return Values

The value rounded to the given precision as a float.

Examples

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)

Changelog

Version Description
5.3.0 The mode parameter was introduced.
5.2.7 The inner workings of round() was changed to conform to the C99 standard.

See Also