Answer by Oleksii Tarbeiev for Round DOWN to nearest half integer in PHP

Here is the solution for integer input.

tests: 124->100, 125->150, 126->150, 187->200, 974->950, 975->1000, 980->1000

function roundHalf($num) {    $rounded = round($num / 50) * 50;    return ($num - $rounded <= 25) ? $rounded : $rounded + 50;}