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Description
$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
precisionis positive, the rounding will occur after the decimal point.If the
precisionis negative, the rounding will occur before the decimal point. If the absolute value of theprecisionis greater than or equal to the number of digits, the result of the rounding is equal to 0 -
mode -
Use one of the following constants to specify the mode in which rounding occurs.
Constants Description PHP_ROUND_HALF_UPRound valup toprecisiondecimal places away from zero, when it is half way there. Making 1.5 into 2 and -1.5 into -2.PHP_ROUND_HALF_DOWNRound valdown toprecisiondecimal places towards zero, when it is half way there. Making 1.5 into 1 and -1.5 into -1.PHP_ROUND_HALF_EVENRound valtoprecisiondecimal places towards the nearest even value.PHP_ROUND_HALF_ODDRound valtoprecisiondecimal places towards the nearest odd value.
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(1.95583, 2));
var_dump(round(1241757, -3));
var_dump(round(5.045, 2));
var_dump(round(5.055, 2));
?>
The above example will output:
float(3) float(4) float(4) float(4) float(1.96) float(1242000) float(5.05) float(5.06)
Example #2 How precision affects a float
<?php
$number = 1346.21;
var_dump(round($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($number, -3));
var_dump(round($number, -4));
?>
The above example will output:
float(1346.21) float(1346.2) float(1346) float(1350) float(1300) float(1000) 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 '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( 1.54, 1, PHP_ROUND_HALF_UP));
var_dump(round(-1.55, 1, PHP_ROUND_HALF_UP));
var_dump(round(-1.54, 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( 1.54, 1, PHP_ROUND_HALF_DOWN));
var_dump(round(-1.55, 1, PHP_ROUND_HALF_DOWN));
var_dump(round(-1.54, 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( 1.54, 1, PHP_ROUND_HALF_EVEN));
var_dump(round(-1.55, 1, PHP_ROUND_HALF_EVEN));
var_dump(round(-1.54, 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( 1.54, 1, PHP_ROUND_HALF_ODD));
var_dump(round(-1.55, 1, PHP_ROUND_HALF_ODD));
var_dump(round(-1.54, 1, PHP_ROUND_HALF_ODD));
?>
The above example will output:
Using PHP_ROUND_HALF_UP with 1 decimal digit precision float(1.6) float(1.5) float(-1.6) float(-1.5) Using PHP_ROUND_HALF_DOWN with 1 decimal digit precision float(1.5) float(1.5) float(-1.5) float(-1.5) Using PHP_ROUND_HALF_EVEN with 1 decimal digit precision float(1.6) float(1.5) float(-1.6) float(-1.5) Using PHP_ROUND_HALF_ODD with 1 decimal digit precision float(1.5) float(1.5) 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
- ceil() - Round fractions up
- floor() - Round fractions down
- number_format() - Format a number with grouped thousands
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Document created the 30/01/2003, last modified the 26/10/2018
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