Hướng dẫn php round always up

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

round — Rounds a float

Description

round(int|float $num, int $precision = 0, int $mode = PHP_ROUND_HALF_UP): float

Parameters

The value to round.

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.

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

Return Values

The value rounded to the given precision as a float.

Changelog

Examples

Example #1 round() examples

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

$number = 135.79;var_dump(round($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

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

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

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

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)

See Also

• ceil() - Round fractions up
• floor() - Round fractions down
• number_format() - Format a number with grouped thousands

takingsides at gmail dot com ¶

8 years ago

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.

function round_up($number, $precision = 2)
{
    $fig = (int) str_pad('1', $precision, '0');
    return (ceil($number * $fig) / $fig);
}

function

goreyshi at gmail dot com ¶

4 years ago

When you have a deal with money like dollars, you need to display it under this condition:
-format all number with two digit decimal for cents.
-divide 1000 by ,
-round half down for number with more than two decimal

I approach it using round function inside the number_format function:

number_format((float)round( 625.371 ,2, PHP_ROUND_HALF_DOWN),2,'.',',')  // 625.37
number_format((float)round( 625.379 ,2, PHP_ROUND_HALF_DOWN),2,'.',',')  // 625.38
number_format((float)round( 1211.20 ,2, PHP_ROUND_HALF_DOWN),2,'.',',')  // 1,211.20
number_format((float)round( 625 ,2, PHP_ROUND_HALF_DOWN),2,'.',',')      // 625.00

depaula at unilogica dot com ¶

5 years ago

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.

/**
* Truncate a float number, example: truncate(-1.49999, 2); // returns -1.49
* truncate(.49999, 3); // returns 0.499
*
* @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/12710283/1596489

slimusgm at gmail dot com ¶

8 years ago

If 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)

serg at kalachev dot ru ¶

8 years ago

Excel-like ROUNDUP function:

public static function round_up($value, $places)
{
    $mult = pow(10, abs($places));
     return $places < 0 ?
    ceil($value / $mult) * $mult :
        ceil($value * $mult) / $mult;
}

echo round_up(12345.23, 1); // 12345.3
echo round_up(12345.23, 0); // 12346
echo round_up(12345.23, -1); // 12350
echo round_up(12345.23, -2); // 12400
echo round_up(12345.23, -3); // 13000
echo round_up(12345.23, -4); // 20000

djcox99 at googlemail dot com ¶

8 years ago

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.

Hayley Watson ¶

3 years ago

It should just be noted that what is called "precision" on this page is more correctly called accuracy; precision is the total number of significant digits on both sides of the decimal point, while accuracy is the number of digits to the right of the point. It's a common confusion.

greghenle at gmail dot com ¶

5 years ago

/**
* 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
*
*/

Mojo urk ¶

4 years ago

Solving round_down() problem:
-----------------------------
Use of (pow(10, $precision) * $value) / pow(10, $precision); ?> fails in some cases, e.g. round_down(2.05, 2) gives incorrect 2.04.
Here is a "string" solution (https://stackoverflow.com/a/26491492/1245149) of the problem (a negative precision is not covered):

function round_down($value, $precision) {       
    $value = (float)$value;
    $precision = (int)$precision;
    if ($precision < 0) {
        $precision = 0;
    }
    $decPointPosition = strpos($value, '.');
    if ($decPointPosition === false) {
        return $value;
    }
    return (float)(substr($value, 0, $decPointPosition + $precision + 1));       
}
?>

Solving round_up() problem:
---------------------------
Use of (pow(10, $precision) * $value) / pow(10, $precision);?> fails in some cases, e.g. round_up(2.22, 2) gives incorrect 2.23 (https://stackoverflow.com/a/8239620/1245149).
Adapting the above round_down() "string" solution I have got this result (a negative precision is not covered):

function round_up($value, $precision) {       
    $value = (float)$value;
    $precision = (int)$precision;
    if ($precision < 0) {
        $precision = 0;
    }
    $decPointPosition = strpos($value, '.');
    if ($decPointPosition === false) {
        return $value;
    }
    $floorValue = (float)(substr($value, 0, $decPointPosition + $precision + 1));
    $followingDecimals = (int)substr($value, $decPointPosition + $precision + 1);
    if ($followingDecimals) {
        $ceilValue = $floorValue + pow(10, -$precision); // does this give always right result?
    }
    else {
        $ceilValue = $floorValue;
    }
    return $ceilValue;               
}
?>

I don't know it is bulletproof, but at least it removes the above mentioned fail. I have done no binary-to-decimal-math-analysis but if `$floorValue + pow(10, 0 - $precision)` works
always as expected then it should be ok.

jongbumi at gmail dot com ¶

6 years ago

PHP 5.3, 5.4, 5.5
$fInfinty = pow(1000, 1000); // float(INF)
$fResult = round(123.456, $fInfinty); // double(123)
?>

PHP 5.6
$fInfinty = pow(1000, 1000); // float(INF)
$fResult = round(123.456, $fInfinty); // float(0)
?>

PHP 7
$fInfinty = pow(1000, 1000); // float(INF)
$fResult = round(123.456, $fInfinty); // null
?>

dastra ¶

10 years ago

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));

craft at ckdevelop dot org ¶

8 years ago

function mround($val, $f=2, $d=6){
    return sprintf("%".$d.".".$f."f", $val);
}

echo mround(34.89999);  //34.90

twan at ecreation dot nl ¶

22 years ago

If you'd only want to round for displaying variables (not for calculating on the rounded result) then you should use printf with the float:

("%6.2f",3.39532); ?>

This returns: 3.40 .

Anonymous ¶

11 years ago

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.

function roundUpTo($number, $increments) {
    $increments = 1 / $increments;
    return (ceil($number * $increments) / $increments);
}
?>

esion99 at gmail dot com ¶

8 years ago

Unexpected result or misunderstanding (php v5.5.9)

echo round(1.55, 1, PHP_ROUND_HALF_DOWN); // 1.5
echo round(1.551, 1, PHP_ROUND_HALF_DOWN); //1.6?>

christian at deligant dot net ¶

10 years ago

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!

$a=3/4;
echo round($a, 2); // 0.75 setlocale(LC_ALL, 'it_IT@euro', 'it_IT', 'it');
$b=3/4;
echo round($b,2); // 0,75
?>

michaeldnelson dot mdn at gmail dot com ¶

12 years ago

This function will let you round to an arbitrary non-zero number.  Zero of course causes a division by zero.

function roundTo($number, $to){
    return round($number/$to, 0)* $to;
}

echo

martinr at maarja dot net ¶

14 years ago

Please note that the format of this functions output also depends on your locale settings. For example, if you have set your locale to some country that uses commas to separate decimal places, the output of this function also uses commas instead of dots.

This might be a problem when you are feeding the rounded float number into a database, which requires you to separate decimal places with dots.

See it in action:
    echo round('3.5558', 2);
    setlocale(constant('LC_ALL'), 'et_EE.UTF-8');
    echo '
'. round('3.5558', 2);
?>

The output will be:
3.56
3,56

php at silisoftware dot com ¶

20 years ago

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:

round(1241757, -3); // 1242000
RoundSigDigs(1241757, 3); // 1240000
?>

Works on negative numbers too. $sigdigs should be >= 0

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;
}
?>

feha at vision dot to ¶

12 years ago

Here is a short neat function to round minutes (hour) ...

function minutes_round ($hour = '14:03:32', $minutes = '5', $format = "H:i")
{
    // by Femi Hasani [www.vision.to]
    $seconds = strtotime($hour);
    $rounded = round($seconds / ($minutes * 60)) * ($minutes * 60);
    return date($format, $rounded);
}?>

You decide to round to nearest minute ...
example will produce : 14:05

Anonymous ¶

5 years ago

Note that PHP 5.3 didn't just introduce $mode, it rewrote the rounding implementation completely to eliminate many kinds of rounding errors common to rounding floating point values.

That's why round() gives you the correct result even when floor/ceil don't.
For example,  floor(0.285 * 100 + 0.5) VS round(0.285*100 + 0.5). First one gives 28, second one gives 29.

More details here: https://wiki.php.net/rfc/rounding

terry at scribendi dot com ¶

18 years ago

To round any number to a given number of significant digits, use log10 to find out its magnitude:

($n, ceil(0 - log10($n)) + $sigdigits); ?>

Or when you have to display a per-unit price which may work out to be less than a few cents/pence/yen you can use:

// $exp = currency decimal places - 0 for Yen/Won, 2 for most others
$dp = ceil(0 - log10($n)) + $sigdigits;
$display = number_format($amount, ($exp>$dp)?$exp:$dp);
?>

This always displays at least the number of decimal places required by the currency, but more if displaying the unit price with precision requires it - eg: 'English proofreading from $0.0068 per word', 'English beer from $6.80 per pint'.

omnibus at omnibus dot edu dot pl ¶

11 years ago

Beware strange behaviour if number is negative and precision is bigger than the actual number of digits after comma.

round(-0.07, 4);

returns

-0.07000000000000001

So if you validate it against a regular expression requiring the maximum amount of digits after comma, you'll get into trouble.

Anonymous ¶

12 years ago

This functions return ceil($nb) if the double or float value is bigger than "$nb.5" else it's return floor($nb)

    function arounds_int($nb) {

             if(!

spectrumcat at gmail dot com ¶

8 years ago

In case someone will need a "graceful" rounding (that changes it's precision to get a non 0 value) here's a simple function:

function gracefulRound($val, $min = 2, $max = 4) {
    $result = round($val, $min);
    if ($result == 0 && $min < $max) {
        return gracefulRound($val, ++$min, $max);
    } else {
        return $result;
    }
}

Usage:
$_ = array(0.5, 0.023, 0.008, 0.0007, 0.000079, 0.0000048);
foreach ($_ as $val) {
    echo "{$val}: ".gracefulRound($val)."\n";
}

Output:
0.5: 0.5
0.023: 0.02
0.008: 0.01
0.0007: 0.001
0.000079: 0.0001
0.0000048: 0

maxteiber at gmail dot com ¶

15 years ago

the result of this function always depends on the underlying C function. There have been a lot of compiler bugs and floating-point precission problems involving this function. Right now the following code:

echo round(141.075, 2);
?>

returns:

141.07

on my machine.
So never really trust this function when you do critical calculations like accounting stuff!
Instead: use only integers or use string comparisons.

Anonymous ¶

5 years ago

This function has strange. behaviors:

echo round(0.045, 2);      // 0.05
echo round(0.45, 1);      // 0.5
echo round(1.045-1, 2);    // 0.04 !!!
echo round(1.45-1, 1);      // 0.5

Astro ¶

2 years ago

Okay, final version of my function:

function NumberPrecision($n, $precision=0, $is_round=true)
            {
            if ($is_round)
                {
                $r = 5 * pow(10, -($precision+1));
                $n += (($n < 0) ? -$r : $r);
                }

                        $comma = '.';

                        $r = 5 * pow(10, -($precision+2));
            $n += (($n > 0) ? -$r : $r);
            $n = number_format($n, $precision+1, $comma, '');

                        $n .= $comma;
            list($n, $frac) = explode($comma, $n, 2);
            $n = rtrim(rtrim($n, $comma) . $comma . substr($frac, 0, $precision), $comma);
            return ($n);
            }

It can be useful in come cases when built-in function like round() or number_format() returns unexpected results. Works with positive and negative numbers, zero, numbers like 1/12, 0.3, numbers in scientific notation etc.

lossantis at ig dot com dot br ¶

12 years ago

Since the mode parameter for options like PHP_ROUND_HALF_UP is available as of PHP 5.3, here is an alternative for ceiling:

echo 252 / 40; // 6.3 ?>

If I round this:

echo round(252 / 40); // 6 ?>

You can also use a ceil (which might be useful for pagination):

echo ceil(252/40); // 7 ?>

[Edited by: for clarity]

php at persignum dot com ¶

7 years ago

Because this function is missing round up and round down constants and the top note doesn't really show you how to round up or down to the nearest number, here is an easy way to always round up or always round down to the nearest number.

int is the number you want to round

n is the nearest number you want rounded to.

Round up to the nearest number

function round_up($int, $n) {
    return ceil($int / $n) * $n;
}

And to round down to the nearest number

function round_down(int, $n) {
    return floor($int / $n) * $n;
}

Bevan ¶

12 years ago

Formats a number to the specified number of significant figures.

/**
* Formats numbers to the specified number of significant figures.
*
* @author Bevan Rudge, Drupal.geek.nz
*
* @param number $number
*   The number to format.
* @param integer $sf
*   The number of significant figures to round and format the number to.
* @return string
*   The rounded and formatted number.
*/
function format_number_significant_figures($number, $sf) {
  // How many decimal places do we round and format to?
  // @note May be negative.
  $dp = floor($sf - log10(abs($number)));
  // Round as a regular number.
  $number = round($number, $dp);
  // Leave the formatting to format_number(), but always format 0 to 0dp.
  return number_format($number, 0 == $number ? 0 : $dp);
}
?>