round
(PHP 4, PHP 5, PHP 7, PHP 8)
round — 對浮點數進行四捨五入
說明
$val, int $precision = 0, int $mode = PHP_ROUND_HALF_UP): float
返回將 val 根據指定精度
precision（十進制小數點后數字的數目）進行四捨五入的結果。precision
也可以是負數或零（預設值）。
參數
-
val -
要處理的值。
-
precision -
可選的十進制小數點后數字的數目。
If the
precisionis positive,valis rounded toprecisionsignificant digits after the decimal point.If the
precisionis negative,valis rounded toprecisionsignificant digits before the decimal point, i.e. to the nearest multiple ofpow(10, -precision), e.g. for aprecisionof -1valis rounded to tens, for aprecisionof -2 to hundreds, etc. -
mode -
Use one of the following constants to specify the mode in which rounding occurs.
常量 說明 PHP_ROUND_HALF_UPRounds valaway from zero when it is half way there, making 1.5 into 2 and -1.5 into -2.PHP_ROUND_HALF_DOWNRounds valtowards zero when it is half way there, making 1.5 into 1 and -1.5 into -1.PHP_ROUND_HALF_EVENRounds valtowards the nearest even value when it is half way there, making both 1.5 and 2.5 into 2.PHP_ROUND_HALF_ODDRounds valtowards the nearest odd value when it is half way there, making 1.5 into 1 and 2.5 into 3.
返回值
The value rounded to the given precision as a float.
範例
示例 #1 round() 例子
<?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));
?>
以上例程會輸出：
float(3) float(4) float(4) float(4) float(5.05) float(5.06) float(300) float(0) float(700) float(1000)
示例 #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));
?>
以上例程會輸出：
float(135.79) float(135.79) float(135.8) float(136) float(140) float(100) float(0)
示例 #3 mode 例子
<?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));
?>
以上例程會輸出：
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)
示例 #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));
?>
以上例程會輸出：
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)