Rounding down numbers to set points with PHP - php

Question

I have a basic 5 star rating system based on user submissions. depending on the rating, a particular image is shown.
$user_rating contains the rating number to one decimal place.
There are 'star' images with
0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0
in the file names.
I need whatever number is contained in $user_rating to be rounded down to the nearest value above and stored in a new variable $star_rating. The numbers can never be rounded up. Even if $user_rating is 4.9, $star_rating should be 4.5.
Can someone help me achieve this?
Thanks
EDIT - using this but just returns original value - in this case 3.8
$star_rating = $user_rating;
function roundToHalf($star_rating) {
$temp = $star_rating * 10;
$remainder = $star_rating % 5;
return ($temp - $remainder) / 10;
}

Answer 1

<?php
function roundRating($rating, array $ratings)
{
if (in_array($rating, $ratings))
{
return $rating;
}
foreach($ratings as $key => $value)
{
if ($value > $rating)
{
return $ratings[($key - 1)];
}
}
return FALSE;
}
$ratings = array(0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0);
$rating = 4.3;
if ($rate = roundRating($rating, $ratings))
echo sprintf('%.01f', $rate);
Demo: http://3v4l.org/BRBne

Answer 2

A simple approach:
function roundToHalf($star_rating) {
return floor( $star_rating * 2 ) / 2;
}
This works because you're looking values evenly divisible by .5 . The result is a float. I think you're better off getting back a numerical value, in case you want to use it for mathematical purposes. Let your display code format it as needed.

Answer 3

function roundDownToHalf($number) {
$remainder = ($number * 10) % 10;
$half = $remainder >= 5 ? 0.5 : 0;
$value = floatval(intval($number) + $half);
return number_format($value, 1, '.', '');
}
define("ENDL", "\n");
print roundDownToHalf(4.9) . ENDL;
print roundDownToHalf(4.5) . ENDL;
print roundDownToHalf(3.8) . ENDL;
print roundDownToHalf(2.3) . ENDL;
print roundDownToHalf(1.0) . ENDL;
print roundDownToHalf(0.6) . ENDL;
Output
4.5
4.5
3.5
2.0
1.0
0.5
All in one compact function:
function roundDownToHalf($n) {
return number_format(floatval(intval($n)+((($n*10)%10)>=5?.5:0)),1,'.','');
}

Answer 4

Multiply by 10 to make it into an integer than use the modulus operator '%' to remove the remainder. Then divide by 10 to make it back into a decimal.
function roundToHalf($number) {
$temp = intval($number * 10);
$remainder = $temp % 5;
return ($temp - $remainder) / 10;
}