Mastering PHP’s round() Function: Precise Rounding Techniques

The round() function in PHP returns the value of a number rounded to a specified precision, optionally using a chosen rounding mode.

Syntax:

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

Parameters $val – the number to be rounded. $precision – optional; the number of decimal digits to round to. It can be zero, positive, or negative. $mode – optional; one of the constants PHP_ROUND_HALF_UP, PHP_ROUND_HALF_DOWN, PHP_ROUND_HALF_EVEN, or PHP_ROUND_HALF_ODD, defining how .5 values are handled.

Return value

The function returns the rounded number as a float.

Examples

<?php
echo round(3.4);               // 3
echo round(3.5);               // 4
echo round(3.6);               // 4
echo round(3.6, 0);            // 4
echo round(1.95583, 2);        // 1.96
echo round(1241757, -3);       // 1242000
echo round(5.045, 2);          // 5.05
echo round(5.055, 2);          // 5.06
?>

These examples illustrate default rounding (half up) and how specifying precision or a negative precision affects the result.