ClosestValue.php

<?php
function getClosest($needle, $haystack, $highestOnEqual = true) {
    if ($highestOnEqual === true) {
        rsort($haystack, SORT_NUMERIC);
    } else {
        asort($haystack, SORT_NUMERIC);
    }
    $value = current($haystack);
    foreach ($haystack as $val) {
        if (abs($needle - $value) > abs($val - $needle)) {
            $value = $val;
        }
    }
    return $value;
}