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PHP round() Function
The round() function proves useful in rounding any floating point number up to a desired precision level. Positive precision parameter causes the number to be rounded after decimal point, whereas with negative precision, rounding occurs before decimal point. Precision is 0 by default.
For example, round(10.6) returns 11, round(10.2) returns 10. The function always returns a floating point number.
Syntax
round(float $value, int $precision = 0, int $mode = PHP_ROUND_HALF_UP): float
Parameters
| Parameter | Description |
|---|---|
| value | A float number to be rounded |
| precision | Number of decimal digits to round to. Default is 0. Positive precision rounds after decimal point. Negative precision rounds before decimal point. |
| mode | Rounding mode using predefined constants (see below) |
Rounding Modes
| Constant | Description |
|---|---|
| PHP_ROUND_HALF_UP | Rounds away from zero when halfway. 1.5 becomes 2, -1.5 becomes -2 |
| PHP_ROUND_HALF_DOWN | Rounds toward zero when halfway. 1.5 becomes 1, -1.5 becomes -1 |
| PHP_ROUND_HALF_EVEN | Rounds to the nearest even number |
| PHP_ROUND_HALF_ODD | Rounds to the nearest odd number |
Basic Examples
Here are basic rounding examples with different precision values ?
<?php
echo "round(3.456) = " . round(3.456) . "<br>";
echo "round(3.456, 1) = " . round(3.456, 1) . "<br>";
echo "round(3.456, 2) = " . round(3.456, 2) . "<br>";
echo "round(1234.5, -1) = " . round(1234.5, -1) . "<br>";
echo "round(1234.5, -2) = " . round(1234.5, -2) . "<br>";
?>
round(3.456) = 3 round(3.456, 1) = 3.5 round(3.456, 2) = 3.46 round(1234.5, -1) = 1230 round(1234.5, -2) = 1200
Rounding Mode Examples
Different rounding modes affect how halfway values are handled ?
<?php
echo "round(3.5, 0, PHP_ROUND_HALF_UP) = " . round(3.5, 0, PHP_ROUND_HALF_UP) . "<br>";
echo "round(3.5, 0, PHP_ROUND_HALF_DOWN) = " . round(3.5, 0, PHP_ROUND_HALF_DOWN) . "<br>";
echo "round(3.5, 0, PHP_ROUND_HALF_EVEN) = " . round(3.5, 0, PHP_ROUND_HALF_EVEN) . "<br>";
echo "round(3.5, 0, PHP_ROUND_HALF_ODD) = " . round(3.5, 0, PHP_ROUND_HALF_ODD) . "<br>";
?>
round(3.5, 0, PHP_ROUND_HALF_UP) = 4 round(3.5, 0, PHP_ROUND_HALF_DOWN) = 3 round(3.5, 0, PHP_ROUND_HALF_EVEN) = 4 round(3.5, 0, PHP_ROUND_HALF_ODD) = 3
Return Values
PHP round() function returns a float number by rounding the value to desired precision.
Conclusion
The round() function is essential for controlling decimal precision in calculations. Use positive precision for decimal places and negative precision for rounding to tens, hundreds, etc.
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