php - How to round to nearest Thousand?

Question

How Do I round a number to its nearest thousand?

function round($var) {
    // Round it
}

Answer 1

PHP allows negative precision for round such as with:

$x = round ($x, -3); // Uses default mode of PHP_ROUND_HALF_UP.

Whereas a positive precision indicates where to round after the decimal point, negative precisions provide the same power before the decimal point. So:

n    round(1111.1111,n)
==   ==================
 3   1111.111
 2   1111.11
 1   1111.1
 0   1111
-1   1110
-2   1100
-3   1000

As a general solution, even for languages that don't have it built in, you simply do something like:

• add 500.
• divide it by 1000 (and truncate to integer if necessary).
• multiply by 1000.

This is, of course, assuming you want the PHP_ROUND_HALF_UP behaviour. There are some who think that bankers rounding, PHP_ROUND_HALF_EVEN, is better for reducing cumulative errors but that's a topic for a different question.