Rounding down numbers to set points with PHP -

i have basic 5 star rating system based on user submissions. depending on rating, particular image shown.

$user_rating contains rating number 1 decimal place.

there 'star' images

0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0

in file names.

i need whatever number contained in $user_rating rounded down nearest value above , stored in new variable $star_rating. numbers can never rounded up. if $user_rating 4.9, $star_rating should 4.5.

can me achieve this? thanks

edit - using returns original value - in case 3.8

$star_rating = $user_rating;    function roundtohalf($star_rating) {      $temp = $star_rating * 10;      $remainder = $star_rating % 5;      return ($temp - $remainder) / 10;  } 

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 1 compact function:

function rounddowntohalf($n) {   return number_format(floatval(intval($n)+((($n*10)%10)>=5?.5:0)),1,'.',''); }